ACOM 1010 Introductory IT Skills
Introduction to Excel (Science students)
Lecture 6
Introduction to Excel for Science Students
The focus on this handout is on the use of the Excel spreadsheet (part of the Microsoft Office XP
suite). When you have worked through this handout you can expect to have acquired general familiarity but
more specifically to be competent in the use of Excel up to a level where you can use the standard features;
entering and formatting data, but also some more advanced features, such as basic formulas and creating
charts. Excel is an extremely powerful package and there is plenty more to be learned about it than can be
covered here. If you wish to take it further then the ACOM optional component on Data Handling and
Presentation will be an excellent place to start.
There are two versions of this handout, which cover similar ground (and indeed have a good deal of
material in common), but which differ from each other in having a slightly different style and academic focus.
This version, entitled Introduction to Excel for Science Students, is intended primarily for students in the
sciences and accordingly takes its worked examples from scientific data. Students in non-technical
disciplines who would prefer an approach that confines its examples to historical and social data should
consult instead the alternative version, Introduction to Excel for Humanities Students.
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ACOM 1010 Introductory IT Skills
Introduction to Excel (Science students)
Lecture 6
What is a Spreadsheet?
One of the things for which computers are particularly useful is the handling of repetitive calculations,
because unlike us they don’t get bored, irritated, distracted or careless. For example, if as a teacher you
have 300 students on a course with three pieces of coursework and you want to calculate the average
mark for each student, it would take an afternoon to do by hand and you’d almost be able to guarantee
some errors. Furthermore, if the data changed in any way, you would have to recalculate everything
relating to the changed data. To do these sorts of job on a computer you would be well advised to use a
spreadsheet, which is a tool that makes such tasks very easy to do, won’t make any mistakes, and will take
seconds (at least once you’ve entered the data). In a simple spreadsheet, data are arranged in a grid with
each “cell” (i.e. box of the grid) containing a single numerical value. Calculations can be performed on
whole rows or columns of numbers. If you change the value of any of the numbers in a spreadsheet, all
calculations referring to that number will be redone taking into account the change. This means that once
set up, spreadsheets can be used to model the effects of changes on whole systems. Although
spreadsheets started out as tools in accountancy (as a means of doing the many boring sums that are
required to keep a balance sheet) they can now do much more than add up. In this handout, you will be
taken through using a spreadsheet to make calculations, produce charts, and carry out some simple
statistical functions, and will also learn how to incorporate charts into a Word document.
Getting Started: Setting up Excel
The Spreadsheet package that you will be using is called Excel. It is a very powerful package, and we will
only scratch the surface of its capabilities in this handout. Microsoft Excel can be run from the
Windows desktop. To start Excel, either double click on the desktop icon, or select Excel from
the Start button on the task bar, and go to Programs | MS Office XP
When Excel has loaded, you should see the main Excel window, showing an empty spreadsheet
(appearing as a grid of labelled rows and columns, with the title “Book1” across the top). On the right hand
side of the window is the “New Workbook” Task Pane which allows you to create a new blank workbook or
to open an existing workbook. After you have done so, the Task Pane will automatically close (or you can
close it yourself by clicking on the “X” button on the top right of the window). The task pane can be opened
again from the View menu. The screen should look like the picture on the following page. If for any reason
it doesn’t, call up the View menu (by clicking on the word “View”) and check that there is a tick next to the
“Formula Bar” item on this menu – if there isn’t, click on that item. Also in the View menu, click on
“Toolbars...” and check that the “Standard” and “Formatting” have been selected.
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ACOM 1010 Introductory IT Skills
Introduction to Excel (Science students)
Lecture 6
The Excel window upon opening
Workbooks, Worksheets and Cells
Excel organises data into “workbooks”, each of which can contain a number of (usually related)
spreadsheets – Excel calls each spreadsheet within a workbook a “worksheet”. This means that you can
have many spreadsheets easily accessible within the program at the same time, making it very easy to
copy data from one to another, or to have one spreadsheet linked to the results of calculations carried out
on another spreadsheet. When you save an Excel workbook, all spreadsheets contained within that
workbook are saved into the same file. To begin with, however, we shall use only the first “sheet” of the
workbook.
When you start up Excel, even though you haven’t asked for a new file, a blank workbook (usually
called “Book1”) is opened, with the first blank worksheet of that workbook (“Sheet1”) displayed. This looks
like an empty grid, with letters across the top and numbers down the left-hand side. A spreadsheet
consists essentially of just that, a grid of cells, which are organised into columns and rows. Each column is
referred to by a letter, and each row by a number. Each individual cell can be identified by specifying its
column and row – e.g. the top left-hand cell is A1 (always specify the column first). Along the bottom of the
screen are a number of labelled “tabs”, like those on index cards, which say “Sheet1”, “Sheet2” etc. These
select the separate worksheets available in the open workbook. To move from one worksheet to another,
you simply click on the tab referring to the one you want.
For the moment, you don’t actually need an empty workbook, because you are going to cover the
basics of Excel using a spreadsheet that’s already been created for you. Closing a
file in Excel is exactly the same as in most other Windows applications – use the left
mouse button to select the File menu, and then move the mouse down to the
“Close” item on that menu (as pictured here) before releasing the button. When
you’ve done this the Excel window will become a lot simpler as there is no longer an active file.
You will now need to download the example file that is needed to complete the exercises in this
handout. It is available from the Teaching Materials page on the ACOM web site. Select the line
appropriate to this handout– “Hawdat.xls” – and the file you require will be copied to your home directory.
Once you have downloaded the file, there should be no need to do so again.
When you have the relevant file in your home directory, go again to the File menu in Excel and select
“Open...”. A dialogue box will appear, very much like the Open File dialogue box in Word. Assuming that
your home directory is selected, names of the files that you have copied over should appear somewhere in
the list box on the left of the Open File window, and amongst these should be “hawdat.xls ”. If you can’t
see this you probably need to change drives in order that the files on your “home” disk area are shown: to
change drives, click on the ò symbol to the right of where it says “Drives” and scroll up or down in the
resulting menu until you can see, and click on, “m:\”.
When “hawdat.xls” does appear in the Open File list box, highlight it and then click on “OK” – the
Excel window should then look like the picture on the next page (though in order to illustrate how an active
cell appears, this picture shows the spreadsheet after the mouse has been clicked on the cell B2).
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ACOM 1010 Introductory IT Skills
Introduction to Excel (Science students)
Lecture 6
The Excel Window on loading HAWDAT.XLS
When using an Excel spreadsheet, most of the time there will be one “active” (and “selected”) cell.
Such a cell has a darker border than all the other cells, and also has a small dark square in the bottom
right-hand corner. Also, the “address” of the active cell (e.g. “B2”) is shown at the left of the Formula Bar,
which runs across the top of the Excel window just under the toolbars, and the contents of the active cell
are shown in the remainder of the Formula Bar. When adding or altering data, only the active cell can be
changed, but you can make any cell you want become the active cell using either the mouse or the
keyboard. Using the mouse, simply click once on the cell that you want to make active. Using the keyboard,
move to the cell you want to make active by using the arrow keys. There is a shortcut for making the top
left cell (A1) active – simply press the Home key whilst holding down the CTRL key.
Later in the handout you will see how it is possible to select more than one cell at a time, in order for
example to format them all in one operation or to move their contents around together – these groups of
selected cells will usually form a rectangular array. However in such cases the Formula Bar will still show
the address and contents of a single “active” cell amongst the group (usually the top left cell in the array),
and if you now type some data in it will be only that one active cell which is affected. So although a cell
being “active” and being “selected” come to much the same thing whenever you’re dealing with a single cell,
there is a distinction between them when a number of cells are involved – many cells can be selected
together, but only one can be active.
Layout and Text Formatting
The spreadsheet HAWDAT.XLS contains data on the Hawaiian-Emperor chain of volcanoes.1 As you can
see, it is not particularly well organised, and moreover contains a few typing errors, notably in the heading.
1 This spreadsheet is based upon results quoted in Table 1 of the paper “Volcanic periodicity along the Hawaiian-Emperor chain”
by Herbert R. Shaw, E. Dale Jackson and Keith E. Barger, American Journal of Science 280a (1980), pp. 667-708.
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ACOM 1010 Introductory IT Skills
Introduction to Excel (Science students)
Lecture 6
Changing Column Widths
The first thing to do to this spreadsheet is to change the width of the columns so that all of the text
becomes readable. To do this, position the mouse pointer between two column selectors at the top of the
spreadsheet (for example, A and B). Then move it around a little if necessary until it becomes a line with a
horizontal arrow coming out of each side. When it is a two-headed arrow, hold down the left mouse button
and (slowly) move the mouse to the right. The column on the left should become larger, and all of the
columns to the right of it should move along to make space without themselves changing in size.
Try this out in the spreadsheet HAWDAT.XLS, arranging the column widths so that all the writing in
column A and the headings in columns B, C, and D are fully visible. You will notice that when the cell(s) to
the right of a cell containing text are empty, Excel allows the text to run over into the next cell so you don’t
need to adjust the column width to see its entire contents. An example of this is the heading in Row 1 of
the spreadsheet HAWDAT.XLS.
Changing Font Size
To make the spreadsheet HAWDAT.XLS easier and clearer to use, we can highlight the heading by
changing the font size and by making it bold or italic, just as in Word documents.
To do this in Excel, move the mouse over the cell in which you wish to change the formatting. The
mouse pointer should become a chunky cross. Click once on the cell – this should select it, so that it
appears with a thicker border. When you have done this, click on the Bold button, which should be on one
of the toolbars across the top of the screen (if it isn’t, please refer to the section on setting up Excel on
page 2). As with Word, there are three buttons for text formatting: Bold, Italic and Underline. Also like
Word, there is a font type box and a font size box. These character formatting options all apply to the
selected cell(s). If you wish to select more than one cell, you can hold down the left mouse button (but only
when the mouse pointer is a chunky cross) and drag the pointer over the cells you wish to select. This has
the effect of selecting a rectangular array of cells, which then appear with a thick border around the entire
selection. In this way, you can select groups of cells for text formatting (and as you will
find out later, calculations). You can also select whole rows and columns by clicking on
the row or column selector buttons (e.g. the “A”, “B”, “C”, “1”, “2” and “3” buttons – being
able to do this is particularly useful if you wish, say, to centre an entire column, or to italicise or embolden
an entire row).
Inserting Rows and Columns
Excel has a very useful shortcut menu, the contents of which change depending upon what part of a
spreadsheet you are in and what cells are selected at the time you call the menu up. To see this shortcut
menu, select a cell (or cells) and click on the right mouse button. This menu is particularly useful when
you want to insert rows or columns.
To insert a column, click once on the selector of the column where you would like the new blank
column to be inserted – this will highlight that column. Then either click once on the right mouse button
and select “Insert” from the resulting menu, or click on the Insert menu (from the standard Menu Bar along
the top of the screen) and select Column from there.
A similar technique applies for inserting rows: highlight the row where you want the new blank row to
go (by clicking once on its row selector) and then use either the right mouse button menu or the Insert
menu to insert the new row. Notice that when you insert a new blank column or row the existing column or
row at that position is not overwritten, but instead moves along or down to make space for the insertion.
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ACOM 1010 Introductory IT Skills
Introduction to Excel (Science students)
Lecture 6
In the spreadsheet HAWDAT.XLS, insert another row now beneath the rows containing the headings
(i.e. beneath row 4), by clicking with the left mouse button on row selector 5, then with the right mouse
button to call up the shortcut menu, and finally select “Insert” from that menu.
Aligning Text and Numbers
In Excel, numbers are initially automatically aligned at the right of a cell and text at the left. 2 However, you
will not necessarily want to stick with these default alignments.
To practise changing the alignment of some cells, select the entire array of numbers in the
spreadsheet HAWDAT.XLS by dragging the mouse (when the pointer is a chunky cross) from cell B6 to cell
D24. Next, click on the Centre button on the formatting toolbar. The contents of the selected cells will now
become centred.
There is one alignment button on the Excel toolbars which you will not recognise from Word - this
button (pictured on the right here) allows you to centre an item of text across a range of cells
(treating them for this purpose as though they were a single cell), and can be particularly useful for
headings. To use this function, highlight the relevant range of cells (which should include the text
you wish to centre) and then click on the button.
Adding Borders
One further way in which the presentation of an Excel spreadsheet can be improved is by adding borders
around specific cells. Borders can function like underlining, helping to identify titles and table headings, or
they can be used to clarify the structure of a spreadsheet by enclosing related information in boxes. You
can put a border all round a cell, or along any selected sides of it. As with text formatting, the application of
borders applies only to the cell or cells which are currently selected. To add a border to a cell or array of
cells, select the cell or cells by dragging the mouse, and then click on the ò button next to the Borders
button on the Formatting Toolbar. A selection of border types will appear – as you can see from the picture,
you can have single line borders, borders consisting of two lines, thick borders, thin borders, and a variety
of other choices. And you can have borders at the right- or left-hand side of the active cells as well as the
top and bottom. To test out using borders in a spreadsheet, highlight the table headings in row 4 of the
spreadsheet HAWDAT.XLS, and give them a thin border along the bottom of the cells. Next highlight the
row headings in column A of the spreadsheet, and give these cells a thin border along their right edge.
Entering and Editing Data
To enter new data into an Excel spreadsheet, click on the (presumably empty) cell in which you wish to
enter it, and then simply type the data into that cell. You will see the characters you type appear
simultaneously in two places in the Excel window – within the actual cell that you’ve selected, and on the
Formula Bar across the top of the open spreadsheet. The data you enter is not finalised until you do one of
three things: press Enter, press one of the arrow keys, or click on the green tick that appears on the
Formula Bar while you type. Until you do one of these things, pressing Escape or clicking on the red cross
on the Formula Bar will make whatever you have typed disappear. It may seem overly complicated to have
three different ways to do the same thing, but each of the methods is useful in different situations. If you
are typing in a whole column of numbers, using the downarrow or the Enter key means that you don’t
have to move from the keyboard to the mouse in order to finalise the cell contents. However, if you are
moving around entering numbers in different parts of the spreadsheet, using the mouse to finalise the
entries can be useful as you are likely to be using it anyway to move from one part of the spreadsheet to
2 This gives a handy way of knowing when you have typed in a number incorrectly: if you have accidentally included a non-numeric
character in a number, it will come up aligned to the left, not the right.
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ACOM 1010 Introductory IT Skills
Introduction to Excel (Science students)
Lecture 6
another. Try entering new text now, by typing the word “Average” into cell A25 of the spreadsheet
HAWDAT.XLS. (Cell A25 should be the first empty cell below the volcano names.)
Sometimes you will want to replace data that is already entered. This is very easy with Excel,
because whatever you type into a cell just replaces whatever was there previously, so you can simply treat
any cell with old data in it the same way as if it were empty cell. In the spreadsheet HAWDAT.XLS, one of
the cells contains incorrect data: it reads “1000” when it should read “103” (this was originally cell B7, but
should now be cell B8). Click on this cell and type “103”, then either press Enter, press one of the arrow
keys or click with the mouse on the green tick. You will then see that the contents of the cell have changed
accordingly.
To edit data already entered within a cell but without totally replacing the contents of the cell (e.g. if
the cell contains text, or a complicated formula which you want to modify without typing it all out again), first
make the cell you wish to edit the active cell, when you will notice that its contents appear on
the Formula Bar at the top of the screen. Then move the mouse over the Formula Bar until
the pointer of the mouse becomes an I-bar (a pointer shaped like a capital “I”, as in the
picture here). Click once on the text on the Formula Bar, and a cursor will appear where you
have clicked. You can now edit this text in the usual manner making use of the arrow keys, Backspace,
Delete and so on. When you have finished, either press Enter or click on the green tick to finalise your
changes. Try this out now, by correcting the typing error (“Enporer”) in the heading of HAWDAT.XLS. Click
on cell A1, then click on the Formula Bar in the region of the “Enp” and correct this to “Emp”.
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ACOM 1010 Introductory IT Skills
Introduction to Excel (Science students)
Lecture 6
Performing Calculations
During this section we will use Excel to perform calculations. To include calculations in your Excel
workbook you can create your own formulas. Formulas are mostly used to perform calculations such as
additions, subtractions, multiplication and divide. More complex functions can be carried out but these are
not covered here.
To perform a calculation in Excel, you have to enter a Formula. Formulae in Excel start with an equals
sign: this is how Excel knows that a formula is being entered and not just text.
If for some reason you want a cell to contain text that starts with an equals sign, you should type an
apostrophe before the equals so Excel will know it’s not a formula.
Sometimes Excel will convert numeric data that you have entered into dates’ e.g. 10-12 will be converted
into 10th Dec, to stop this happening, prefix the data with an apostrophe to let Excel know that you are
entering numeric data.
Excel can carry out all sorts of calculations – some of the commonest kinds are shown in the table below.
Entering a formula is similar to entering data or text: you first select (and thus make “active”) the cell where
you want the result of the formula to appear, and then you type “=” followed by the calculation that you want
the spreadsheet to perform.
Simple Arithmetical Functions in Excel
Function
Example
Description
*
=A2*A5
Multiplication
/
=A2/A5
Division
+
=A2 + A5
Addition
-
=A2 – A5
Subtraction
Some commonly used Functions in Excel
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Function
Example
Description
SUM
=SUM(A1:A14)
Calculates the total in a range of cells
AVERAGE
=AVERAGE(A4:B5)
COUNT
=COUNT(A4:A19)
Counts the number of cells that hold numerical values in a
group of cells.
MAX
=MAX(A4:A10)
Gives the maximum value in a range of cells
MIN
=MIN(A4:A10)
Enters the minimum value in a range of cells
Calculates the average (or “mean”) of a group of cells
ACOM 1010 Introductory IT Skills
Introduction to Excel (Science students)
Lecture 6
To practise using simple formulae in Excel, we can fill in row 25 of HAWDAT.XLS (which we previously
labelled as the “Average” row) Click on cell B25, and type in “=AVERAGE(B6:B24)”. This formula instructs
Excel to calculate the average of cells B6 to B24. You will notice that when you finalise the contents of cell
B25 (by pressing Enter, pressing one of the arrow keys or clicking on the green tick) the formula you have
typed in still appears on the Formula Bar but the result of the formula now appears in the cell.
You’ll see from the table above that the formula for the sum of a range of cells has a similar syntax to
the formula for an average, but because summing rows and columns is one of the most common types of
calculation, if you do want to enter a “SUM” formula then you can make use of a convenient shortcut that
Excel provides by means of the “AutoSum” button in the Toolbar. If you make a particular cell active and
then click on this button, the active cell will be made to contain a “SUM” formula as though you were in the
process of editing it, thus giving you the opportunity to change the relevant range (or even, as we will see,
the function itself) before finalising the formula. In the present case we don’t actually want to insert a
“SUM”, but as an illustration, click on the cell C25 and then on the AutoSum button – when you do this, the
text “=SUM(C6:C24)“ will appear in the cell C25 with the range “C6:C24” highlighted. This means Excel
has worked out that C6:C24 is probably the range that you want, because it is a contiguous range of cells
directly adjacent to the active cell C25 and all containing straightforward numeric data (not formulae). But
you can if you wish change the formula – do this now by clicking on the word “SUM”, then editing it using
Delete and/or Backspace so that instead the formula reads “=AVERAGE(C6:C24)”. Finally, press Enter
(or click on the green tick on the formula bar) to make Excel accept the finished formula. 3
AutoFill
Excel has a feature called “AutoFill”, which takes formulae or other data that you have typed in and
“spreads” them to adjacent cells, continuing any simple sequence that it finds there (e.g. if you have one
cell containing “Tuesday”, and “spread” this onto adjacent cells downwards or to the right, then AutoFill will
automatically continue the series of days forwards through “Wednesday” etc; while if you spread it upwards
or to the left, AutoFill will continue the sequence backwards through “Monday” etc). AutoFill can have
strange effects if you are not sure what sequence Excel might see in your data, but it can be very helpful
either for applying a similar formula (e.g. a sum) to several adjacent columns, or for filling in quickly a large
number of “label” cells (e.g. to label a table of data).
To use AutoFill, you should first select the cell or cells containing the formula or data that you want to
“spread”, and then move the mouse pointer over the small square in the corner of the selection. The
mouse pointer should become a thin cross, like the one shown on the right here. When this
happens, hold down the left mouse button and drag the cross over the cells that you wish to fill
with the spread formula or data. When you release the mouse button, the cells you have just covered will
be filled accordingly.
Try this now using the spreadsheet HAWDAT.XLS. Make cell C25 (the one in which you most recently
entered a formula) active, and move the mouse pointer over the bottom right corner of this cell until it
becomes a thin cross. Hold down the mouse button and drag the cross over D25 to cell E25 (as you do so,
a thick grey border should enclose the cells over which you move). On releasing the left mouse button, you
will notice that D25 and E25 now contain formulae which are of exactly the same type as the formula in
3 We saw earlier that when a number or formula has been typed straightforwardly into the active cell, clicking elsewhere has much
the same effect as pressing Enter (i.e. it accepts the number or formula in its current state). But in this AutoSum context – where
part of the formula is highlighted – a mouse click within another cell (or a mouse drag over other cells) will be treated as putting a
reference to that cell (or cells) within the formula. A similar point applies if, for example, you type the unfinished formula
“=AVERAGE(“ and then drag the mouse over a range of cells: try it to see what happens. This can be a very convenient technique
for inserting cell references into formulae, but it can also be confusing if you don’t know what to expect!
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ACOM 1010 Introductory IT Skills
Introduction to Excel (Science students)
Lecture 6
C25 but with different column references – hence D25 calculates the average of cells D6 to D24, while E25
calculates the average of cells E6 to E24 (since the cells in column E are empty, however, this gives an
error message). Make sure you’re quite clear about what’s going on here, by clicking once on each of the
cells and chec king what the Formula Bar contains. As you can see, the AutoFill is a great labour-saver
when you want to calculate totals or averages (or whatever) of a number of columns of data – having typed
the formula into one column, you can “spread” it along the row to the others. And the AutoFill can work in
just the same way when it comes to spreading formulae down columns – you’ll see this in action shortly.
To see other effects of AutoFill, select a cell in an empty column of HAWDAT.XLS and type the
number “1”. Then use AutoFill to spread this to a number of other cells lower down in the same column –
you will see that the AutoFill simply copies the “1” that you have typed in into all the cells over which you
drag the thin cross. Now change the second “1” in this column to a “2”. Select the cells containing the first
“1” and the “2” (by clicking and dragging when the mouse is a chunky cross) and then use AutoFill to
replace the rest of the column of “1”s. You will see that something different happens – very useful if you
want to number all the rows of your spreadsheet!
AutoFill is not the only function available when the mouse pointer is a thin cross, for if you drag the
cross in the opposite direction (up or left instead of down or right) you can use it instead to make cells blank.
Select an array of cells (those you just filled with “1”, “2” etc for instance), and move the mouse pointer over
the bottom right corner of the array until it becomes a thin cross. Then hold down the left mouse button, but
instead of dragging the mouse outside the selected cells, drag it inside the selection – you’ll notice that the
cells inside the selection are highlighted in grey as you pass them. When you release the left mouse button,
all of these grey cells will be made empty. 4
One great advantage of using a spreadsheet to set up tables such as the one that we’ve just
completed in HAWDAT.XLS is that if some of the data happen to change, Excel will automatically
recalculate all of the formulae that refer to those data. 5 To watch this happen,
simply change the number in just one of the cells in HAWDAT.XLS, and when you
press Enter (or click in another cell etc), the totals which correspond to that cell
will also change. However we don’t really want to change any of the numbers in
HAWDAT.XLS permanently, so this gives an opportunity to illustrate also the useful
Undo button (pictured on the right). If you click on the Undo button, the last change made will disappear.
This idea should be familiar, because Excel’s Undo button operates just like Word’s, except that,
unfortunately, Excel’s Undo facility can undo only the very last action – it doesn’t remember any
further back than that. Click on Undo now, and whatever number you previously changed will be
changed back.
Now, to reinforce the skills that you have just learned, fill column E of the spreadsheet with
calculations of the percentage uncertainty in the age of each volcano – this means that you must work out
what proportion the “Error” in column D is as a percentage of the “Age” in column C (e.g. in the case of
Kanau Seamount in row 21, the uncertainty or “Error” is 3 million years, which is 7.5% of the estimated
“Age” of 40 million years). If you’re at all unsure of doing this correctly, you might as well take advantage of
the clue in the previous sentence, by clicking on the cell E21 and filling in there the necessary calculation
for the volcano Kanau Seamount (then at least you know what the answer should be!). Remember, since
it’s a formula you’re entering, that it should start with an equals sign, and make use of the cell references
“C21” and “D21” rather than the values that those cells contain. If you need to look up the symbols for
multiplication and division, refer to the table on page 8. Having put the correct formula in cell E21, now use
4 Two other ways of making a selection of cells blank are (a) to select the cells in question and press the Delete key; or (b) to
select them, click on the right mouse button, and choose “Clear Contents” from the shortcut menu.
5 Excel will, not surprisingly, complain if you enter a formula and then change the nature of cells on which the formula is supposed
to operate (e.g. if you enter the formula “=F3+F4” into cell F5, and then edit cell F3 to contain text instead of a number, you’ll get
the error message “#VALUE!” in the cell F5). If you get such error messages and don’t understand what to do about them, consult
Appendix 2 at the end of this booklet.
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ACOM 1010 Introductory IT Skills
Introduction to Excel (Science students)
Lecture 6
the AutoFill to “spread” it first down to cell E24, and then up to cell E6 (observing, as you do these
operations, the effect on the “AVERAGE” formula that you earlier put into cell E25). When you have spread
the formula to cell E6, however, you will probably find that it gives there the error message “#DIV/0!” –
quite rightly, because cell C6 contains zero, and hence the calculation of D6 as a percentage of C6
involves an illegal division by zero (in cases like this, it’s a good idea to keep the spreadsheet tidy by
replacing the formula that generates the error message with an asterisk “*”).6 The “#DIV/0!” error
message is quite self-explanatory, but others can be less obvious (e.g. “#####” would just indicate that the
column is too narrow to display that cell’s contents). If you come across any that you don’t understand,
refer to Appendix 1 at the end of this handout, entitled “Troubleshooting for Formulae”.
Numeric Formats
Having filled in column E, you will probably find that the numbers displayed there are rather untidy, with the
precise Kanau Seamount value appearing as just “7.5”, but all of the “non-round” values being shown to
an accuracy of as many decimal places as will fit into the width of the column (up to a maximum of 10
significant figures). It would obviously be far neater to display all of the figures to the same level of
accuracy, such as one decimal place.
To change the numerical format of some group of cells, first as usual select them with the mouse (so
that a border appears around them), then choose “Cells...” from the Format menu, click on the “Number”
tab within the dialogue box that appears, and click on the word “Number” in the “Category” list down the
left-hand side. Essentially, the point of this dialogue box is to enable you to specify a “Category” and a
“Format Code” for any numerical values that appear in the selected cells. By selecting an appropriate
option from the “Category” list these values can be made to appear as financial amounts, dates, times,
percentages, fractions and so on, but by choosing the “Number” option you have indicated that you want
them to be treated as numbers in ordinary decimal notation (for scientific notation, you would choose the
“Scientific” option). Then, given that they are to be displayed as ordinary decimal numbers, you can select
an appropriate precise format for them by means of the “Decimal Places” list in the middle.
Excel provides a versatile system of numeric format coding, and if you want anything out of the
ordinary you would be well advised to consult the section on “Number Format Codes” in the Excel Help
system (which can be called up either from the Excel Help menu or from the “Help” button in the dialogue
box pictured here).
Returning now to column E, first type a relevant heading into cells E3 and E4 (e.g. “Error” and “%age”
respectively), then select the entire column by clicking on the column selector button at the top – note that
the numeric reformatting you’re about to perform won’t have any detrimental effect on the heading you’ve
just inserted, because that consists of text rather than numbers. Having selected the column, follow the
procedure outlined above to change the numeric format of the column so that it displays numbers to an
accuracy of precisely one decimal place, and then align the numbers in the column to the right, so that the
decimal points all line up neatly. Then when the column is right-aligned you can still ensure that the
numbers don’t appear squashed against the right-hand edge. When you’ve got the numbers looking right,
do a final check that any non-numeric entries in the column (e.g. the headings and the asterisk or error
message in cell E6) are also neatly arranged – you’ll probably find that these look best centred.
6 When you enter the percentage formula into E21, and then when you spread it down to E24, you will notice that the “AVERAGE”
formula in E25 ceases to show the error message “#DIV/0!”, and instead presents, as it should, the average of whatever values
appear above it in the E column. But the same error message reappears for a different reason once the percentage formula has
been spread to E6, because then E25 is attempting to calculate an average with the illegal error value in E6, and this is not allowed.
Replacing the formula in E6 with an asterisk (or any other text) has the advantage of omitting it from the average calculation and
thus avoiding the E25 error message. But if you do this and then look at the values in column E, you’ll see that their average – now
visible in E25 – is pretty misleading and unrepresentative (owing to the overwhelming domination of the Mauna Kea value over
everything else), so it’s probably sensible just to delete the “AVERAGE” formula from E25 in any case. Taking averages doesn’t
always make sense!
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ACOM 1010 Introductory IT Skills
Introduction to Excel (Science students)
Lecture 6
We’ve so far been treating the entries in column E as straightforward numbers, but you should be
able to find an even better way of formatting them if you bear in mind that they are, in fact, percentages. As
an exercise, see if you can do so now by following the same procedure as above except that you select the
“Percentage” rather than the “Number” option from the “Category” list in the Format Cells dialogue box. As
you do this, pay close attention to what results from your reformatting – you should notice that when you tell
Excel to display a number as a percentage, it multiplies the number by 100 for you, so for example “0.5”
appears as “50%”. Hence to display column E as a percentage, you will need to change the formulae in
cells E6:E24 (or E7:E24). See if you can do all this for yourself.
You have now learned how to lay out and format an Excel spreadsheet and the cells within it, to enter
new data, edit old data, carry out reasonably complex calculations and fill in rows and columns with
formulae or data sequences. Now we shall move on to producing graphs and charts. But first, save the
spreadsheet HAWDAT.XLS in its new form, so that if anything goes wrong in what follows you won’t lose the
work that you’ve done so far.
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ACOM 1010 Introductory IT Skills
Introduction to Excel (Science students)
Lecture 6
Using Excel to Produce a Scatter Chart
Using the data in HAWDAT.XLS you are now going to create a scatter chart. The first step in creating a
good chart of any sort is to select the right data – and this is just as true of making a chart in Excel as it is of
making a chart using graph paper and coloured pencils.
One rule of thumb which is useful when thinking about what data to include is that it is usually a bad
idea to include within the same chart both a variety of totals and also the data that make up those totals.
Also, if you want to give a breakdown of a single total, use a pie chart.
As you will have discovered in the previous section, some of the data in the spreadsheet
HAWDAT.XLS are not as reliable as they could be. Where the uncertainty in age is more than
100% of that age, for example, it is obviously reasonable to discard the data as unreliable.
Bearing in mind this point and the point made in the previous paragraph, the area you want to select when
it comes to making a scatter chart out of the data in HAWDAT.XLS is the range of cells B8 to C24. 7 Use the
mouse to select this range of cells now. Having selected them, click once on the ChartWizard button.
“Wizards” in Excel and other Microsoft programs are routines which consist of a series of dialogue boxes
which automate various operations in a simple step-by-step manner. Following the series of boxes in the
case of ChartWizard takes you through the selection of data, the selection of chart type, and whether or not
you want data labels or titles. The end product is a chart of whatever type you want with your chosen
information and labelling.
When you click on the ChartWizard button the first window to appear (the “Step 1” window) asks you
which general chart type you would like. There is a wide range of chart types available in Excel, as you can
see, and it is important to pick an appropriate chart for the data that you are representing. However in
Excel it is very easy to change from one chart type to another, so you
needn’t be too anxious about this – if you’re not sure which chart type
to select, just try out a few before deciding. For the data in
HAWDAT.XLS a scatter chart (called by Excel an “XY (Scatter)” chart)
is probably the most suitable. So click now on the type of chart you
want (the “XY (Scatter)” type has been selected in the picture on the
right here). Excel will display the variety of sub-types available in the
Chart Sub-Type box. Here there are a number of different options, but
which ones are offered will obviously depend on the general chart type
that you have selected. Having decided on a scatter chart, you can for
example choose: whether to have a scatter that compares values, or
with data points connected by smooth lines. It is worth experimenting
with different styles of chart to see which one looks the best for the
data you are using. Do this by selecting your provisional choice (in the picture on the right here, option 1
has been chosen), click the Press and Hold to View Sample button and a larger sample of the chart will be
displayed. When you have selected the chart click on the “Next >” button to continue to the second step of
the ChartWizard, which as we shall see also includes a preview of the finished chart, so if you don’t like the
way the preview looks you can then go back (using the relevant dialogue box’s “< Back” button) and try out
a different general chart type or different chart style. You can carry on flicking between dialogue boxes 2, 3
and 4 in this way, experimenting as much as you like before making your final decision.
7 If you were creating a different type of chart it could be useful to include the column (or row) headings, as with certain types (e.g.
bar charts, histograms and pie charts) Excel can include this information automatically. The easiest way to find out how to produce
different chart types is to experiment (but remember to save the file and to use the Undo button if you don’t want to lose what
you’ve previously done!).
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ACOM 1010 Introductory IT Skills
Introduction to Excel (Science students)
Lecture 6
At this point the selection of cells you made will develop a flashing border and Step 2 of the Chart
Wizard, as well as showing a preview of the finished chart will also ask if the selected cells are indeed
those that you wish to chart. It will say something like “Range: =$B$8:$C$24”. (There is a reason for the
$ signs, to do with absolute cell addressing, but for now we can safely ignore them.) Check that this is the
range you want to chart (i.e. it includes all the reasonable data but not the averages, headings or unreliable
data), then move on. If this window does not display the correct range of cells, you can type in changes by
deleting the range in the window and entering another (in the simpler format of two cell references
separated by a colon, e.g. “=B8:C24”).
Below the Data Range the dialogue box provides a pair of buttons which determine how the data
values are grouped, which can be according to either the Rows or the Columns of the spreadsheet. In our
volcano example you will need to select “Columns” if Excel has not already done so, because in this case
the data are unambiguously arranged in columns rather than rows (i.e. each column contains a single
“homogeneous” kind of data, whereas each row does not), so that selecting “Rows” would give a very
strange effect (try clicking on the “Rows” button now to see what happens, but be sure to change back to
“Columns” before moving on). With other kinds of data, however, particularly those in which rows and
columns provide alternative ways of categorising a single population of objects, it may be the case that
either method of grouping is possible and you may wish to look at both before deciding which is the more
appropriate. When you are happy with the preview, press the “Next”> button to go on to Step 3.
The options in the Step 3 dialogue box gives you further choices regarding the labelling of the chart
(obviously this will depend on the chart type you first selected). The choices of whether to add a chart title
and/or axis titles (here, as you can see, both chart and axis titles have been added), or whether to
remove/include a legend. It is obviously a good idea to
give the chart as a whole a title, if only as a means of
reminding yourself what you have charted. But whether
in addition the chart would benefit from axis titles and/or a
legend is more a matter of discretion. Bear in mind that
too much text can clutter the overall effect, and that the
main purpose of a chart is precisely to put across data in
such a way that overall characteristics which could
otherwise be obscured become obvious. A central
requirement of this is clarity, and if a chart is either overly
or insufficiently labelled this objective will not be achieved.
Note: Excel calls the horizontal (x) axis the “Category” axis and the vertical (y) axis the “value” axis.
The following is a brief description of the remaining spin boxes:
•
Axes tabs would enable you to suppress the display of any of the axes, but you would not generally
want to do this.
•
Gridlines are lines drawn across the chart for visual reference, you can choose which gridlines to
display on your chart by selecting or clearing the Major/Minor gridline check boxes.
•
Legend allow you to show or clear the legend. If you choose to show the legend you can use the
placement buttons to indicate where it should appear.
•
Data Labels you can select a variety of options from the Data Label group
box. E.g. you can choose “Show Value” to have the value of data points
appear on the chart bars associated with them.
•
Data Table tab allows you to show the table of the data from which the chart
was drawn along with the chart.
When you’re quite happy with the sample chart in Step 3 of the ChartWizard, click on “Next”>.
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ACOM 1010 Introductory IT Skills
Introduction to Excel (Science students)
Lecture 6
Step 4 of the Chart Wizard will ask for the Chart Location. You cam select whether to have your
chart appear in a new worksheet or alongside the data it is charting. To insert the chart in a new worksheet
click on “As new sheet” and then click on Finish. Or to have the chart appear alongside the data you are
charting select “As object in”. Then click on Finish.
You will be returned to your spreadsheet, which will now contain the chart you have designed. If this
is too large to fit on the screen or too small to see all the detail, you can re-size it very easily. You will
notice that when the chart first appears the midpoints of its sides, and its corners, are marked with eight
small black squares, indicating that the chart is currently the “active” part of the spreadsheet (so the
squares will disappear if you click on a spreadsheet cell, but will reappear when you again select the chart
by clicking on it). 8 If you move the mouse pointer over one of these squares, the pointer becomes a
double-headed arrow, because the square is actually a “resizing handle”, which can be dragged and
dropped to change the size of the rectangular “chart box” – dragging a side handle will change either the
width or the height of the chart, while dragging a corner handle (diagonally, as indicated by the arrow
direction) will change the chart’s size whilst maintaining the proportion between its width and height (the
picture above shows the bottom right corner handle just about to be dragged). Resizing can be particularly
important if you find that headings or category labels are omitted from your chart – if this happens, it will be
because there’s insufficient room for them, so if you stretch the chart appropriately they should reappear.
When you are content that the chart you have produced is the right size, save the file HAWDAT.XLS.
Creating and Organising a New Spreadsheet
We’ll now work quickly through an example to which a pie
chart is appropriate, but which also brings out some other
aspects of the creation and design of a new spreadsheet. The
data we are going to present in our spreadsheet come from the
following paragraph in the article on "Earth" in the Microsoft
Encarta 97 Encyclopedia.9
“The rocks of the lithosphere have an average density of 2.7 and are
almost entirely made up of 11 elements, which together account for
about 99.5 percent of its mass. The most abundant is oxygen
(about 46.60 percent of the total), followed by silicon (about 27.72
percent), aluminium (8.13 percent), iron (5.0 percent), calcium
(3.63 percent), sodium (2.83 percent), potassium (2.59 percent),
magnesium (2.09 percent) and titanium, hydrogen, and
phosphorus (totaling less than 1 percent). In addition, 11 other
elements are present in trace amounts of 0.1 to 0.02 percent.
These elements, in order of abundance, are carbon, manganese,
sulfur, barium, chlorine, chromium, fluorine, zirconium, nickel,
strontium, and vanadium. The elements are present in the
lithosphere almost entirely in the form of compounds rather than in
their free state. These compounds exist almost entirely in the
crystalline state, so they are, by definition, minerals .”
The data in this paragraph can be displayed to best
advantage in a pie chart, but before we can attempt to do so,
the figures first need to be unravelled a little. Open a new Excel workbook (by selecting “New...” from the
File menu) and make a table listing the elements and their abundance as best you can. You will notice that
titanium, hydrogen and phosphorus have to be treated together as a group, as do the eleven trace
8 Since the chart is selected when it is first created by the ChartWizard, if you decide you don’t want it after all you can erase it
immediately by just pressing the Delete key. The chart can similarly be removed at any other time too, by selecting it and then
pressing the Delete key.
9 Article contributed by Earl Cook. Copyright © 1993-1996 Microsoft Corporation. All rights reserved.
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ACOM 1010 Introductory IT Skills
Introduction to Excel (Science students)
Lecture 6
elements, since in each case the percentage abundance is given for the group as a whole and not for the
individual elements. Moreover the abundance of each of these groups is given only implicitly, and hence
has to be calculated on the assumption that all the percentages should add up to 100% (with all but the
trace elements accounting for 99.5%). You could do these calculations yourself, or insert a relevant
formula, but either way it would be sensible to include at the bottom of the relevant column a “Total” (using
the AutoSum), just to make sure that you’ve got them right. When you’ve done all this, your spreadsheet
might look something like the picture on the right.
In passing, it’s worth noting some things that have been done to tidy this spreadsheet, using the
check box and some of the buttons that are available through the “Alignment” tab of the Format Cells
dialogue box
•
The text in cell A11 has been “wordwrapped” by checking the “Wrap Text” box in the “Alignment” tab of
the Format Cells dialogue box.
•
The text in row 11 has been given a “Centre” vertical alignment using the appropriate button in the
“Alignment” tab.
•
The list of trace elements has been stretched out over the cells A15 to C15 by both checking the
“Wrap Text” box, and clicking the relevant button to give a horizontal alignment of “Centre across
selection”.
Notice also that the numbers in column B have been neatly aligned to the right of the column, being
displayed to two decimal places and with three trailing spaces (using the Number Format Code “0.00
”).
Our table of elements indeed now looks quite presentable, but unfortunately it’s not ideally suited for
producing a pie chart because the labels which it contains (“oxygen”, “silicon” etc) are far too long – in any
pie chart, space is likely to be at a premium, and this will be especially true of one in which some of the
“slices” are extremely thin. So while preserving the full-length labels in column A, it would be advisable to
supplement them with some much shorter labels that can do duty within the chart, and for this purpose the
obvious choices are the standard chemical symbols (“O”, “Si”, “Al”, “Fe” etc) together with straightforward
abbreviations for the two groups of elements (e.g. “Ti/H/P” and “Trace” respectively). However in order for
chart headings or labels to be recognised as such by ChartWizard, they have to be adjacent (on the left or
top) to the data that are being charted. This means that if you want to create a chart, then unless you’ve
already put everything in exactly the right place you may have to move around the numbers and formulae
that you have entered – in the present case, for example, the numeric data need to be moved from column
B to column C, and the abbreviated labels inserted in column B.
Cut, Paste, Drag and Drop Editing
There are several ways to move things around in Excel, of which the most obvious is to use the Clipboard
(much as you would in Word). To do this first select the cell(s) containing the data that you want to move,
then choose “Cut” from the Edit menu (or click on the scissors icon in the Toolbar), 10 then select the cell(s)
to which you want the data moved, and finally choose “Paste” from the Edit menu (or click on the Paste
icon in the Toolbar). 11 Note that with two exceptions, when you Cut (or Copy) data from any array of cells,
you should ensure that the selected destination cell array is of the same dimensions, otherwise Excel will
complain (you can’t, for example, copy a 2x3 array of data into an 3x2 array). The two exceptions are: (a)
when the “source” array is just a single cell, you can Paste its contents simultaneously into as many cells
as you want; and (b) when the “destination” array is just a single cell, the Paste command interprets this as
10 Cut and Paste are also both available on the right mouse button shortcut menu.
11 You may notice that Cut and Paste in Excel do not act in quite the same way as they do in Word – most obviously, when you
perform a Cut the selected cells do not immediately become blank, but instead merely acquire a flashing dotted border. It is not
until you select the destination cells and then Paste (or you can even just press Enter) that the data are moved, being deleted from
the source cells and placed into the destination cells at the same time. Moreover once this has happened those data do not remain
in the Clipboard – unlike Word, the Clipboard in Excel operates only on a transitory basis.
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ACOM 1010 Introductory IT Skills
Introduction to Excel (Science students)
Lecture 6
meaning that pasting should occur to the appropriately sized array of which that single cell is the top-left
corner. (As always, the best way to familiarise yourself with this behaviour is to experiment for yourself.)
Also note that if the destination cells contain data before you do the moving, those data will be overwritten
when it takes place (so make sure that you’re not overwriting information that you wanted to keep).
Another, and often quicker, way of moving text and data around in Excel is by “drag and drop editing”.
With this method, you first select the cells whose data you wish to move, and place the mouse pointer on
the thick border around the edge of the selection – as you do so, the pointer should turn into an arrow.
Then hold down the left mouse button, and drag the border (a grey copy of which will move with the mouse
pointer) to the place where you want the data to be moved. When you have this grey border where you
want it, release the left mouse button and the selected data will move accordingly. As with cutting and
pasting, moving can overwrite the existing contents of the destination cells if they are not empty, but before
overwriting Excel will helpfully display a prompt saying “Replace contents of Destination
Cells?”, which gives you an opportunity either to change your mind (i.e. to “Cancel” the data movement)
or else to confirm that it is “OK” for the existing contents of the cells to be overwritten.
Now use these techniques to rearrange the data in your new spreadsheet so that you have room to
enter the new abbreviated labels into column B. Then insert these labels (consulting the picture on page
18 if you’re unsure of the appropriate chemical symbols). Then, save your new workbook (using the File
menu or the Toolbar Save icon), calling it “ELEMENTS.XLS”.
Creating a Pie Chart using ChartWizard
Creating a pie chart in ChartWizard is very similar to creating a scatter chart. The main thing you have to
consider is the selection of which data fields to include, and as usual, you should not include totals or
averages, but might well wish to include labels.12 In the present case
(assuming that the previous column B values have been moved
horizontally into column C, and that column B now contains abbreviated
labels), the appropriate range will be “B3:C12”, so select the range now
and then call the ChartWizard by clicking on its icon. In the Step 1
dialogue box, select Pie from the Chart type. From the variety of subtypes available in the Chart Sub-Type box, select a sub-type (in the
picture on the right pie with a 3D visual effect has been selected). The
difference between these is purely in their dimensional appearance;
again it is worth experimenting with different styles of chart to see which
one looks the best for the data you are using. Just as we saw when
producing the scatter chart, you should be prepared to experiment by
moving back and forth between the ChartWizard dialogue boxes, trying out a variety of options until you
find a chart that looks good, and that presents the information clearly and efficiently.
Again as we saw in the case of the scatter chart, the Step 2 dialogue box provides a preview of the
chart, and gives an opportunity for checking both that the data are being taken correctly from rows or
columns and the range of cells you are charting is correct. The Step 3 dialogue box allows you to add a
title (desirable) and/or a legend (essential unless the slices are labelled), and any Data Labels such as
values or percentages after which you can click on the “Finish” button to Enter to Excel and view your
completed chart.
12 Excel produces its pie charts by adding up all of the data values selected and working out what proportion of the total each value
represents. Hence it is essential that each data value in the “population” should be counted once and once only, and if you include
totals in your selection you won’t end up with an accurate pie chart. Note, by the way, that although in this case the selected data
values add up to exactly 100, there is no requirement that they do so.
17
ACOM 1010 Introductory IT Skills
Introduction to Excel (Science students)
Lecture 6
Making Alterations to a Finished Chart
You can make alterations to the layout and style of a chart in Excel even when you have finished the
ChartWiz ard. Indeed some such alterations are completely automatic, for just as the results of formulae in
Excel change when the data to which they refer are adjusted, so the contents of a chart will also change
when adjustments are made to the underlying data – you can try this out now by adjusting any of the values
used in the construction of the pie chart (but bear in mind as you do so that the Excel Undo “remembers”
only one operation). Other alterations can be selected using buttons and menus, using the small “floating”
toolbar which appears whenever a chart is selected (i.e. when the mouse is clicked on the chart, and it
acquires those small black squares around the edge). 13 In the picture of the toolbar below, the button
representing a legend is depressed: this means that the active chart features a legend. If you click on this
button the legend should disappear, and likewise if you click on it when it’s not depressed, a legend will
(re)appear. The Chart Toolbar displays nine buttons allowing you to modify different parts of the chart.
And finally the Chart Type button allows you to change the type of chart: if you click on the ò button a
menu of the available basic chart types will appear
and you can simply select from them (but be warned
– you may not be able to Enter to your original chart
if you experiment with all this, so it’s a good idea to save your worksheet first, or else to use Undo after
each and every “experiment”).
As well as the options offered by this toolbar, you can edit any part of a chart manually – to do so, first
double-click on some item in the chart, when it should acquire a thick diagonally striped border (as in the
picture below). Then the options available will depend on the nature of the chart, and you may just have to
experiment to get a feel for the possibilities (don’t worry about this, because most hand-editing operations
are equally easy to undo by hand). Here we’ll begin by focusing on a few of the main editing facilities
relevant to pie charts, because this type of chart that you are most likely to need to edit (to avoid cluttered
labels etc, as mentioned earlier).
Clicking on the chart title will enable you to edit it as text in the usual manner. Clicking on the pie
itself highlights it (i.e. surrounds it with black square “handles”), and you can then drag the mouse to make
all the slices of the pie come apart. If you want to emphasise one particular pie slice, you can click on just
that slice so that it alone becomes highlighted, and then drag that slice away from the rest of the pie.
Selecting a small slice can be fiddly – here the best thing to use is not the mouse but the left (or the right)
arrow key on the keyboard, which will cycle
through the chart’s components in turn and thus
eventually select the slice you want. You can also
select any chart label in this way, and then use
the mouse to move or delete it if necessary (as is
being done in the picture here). 14 Double-clicking
on any part of a chart brings up a new window
with options to change the colours, fill patterns or
other features depending on the chart type and
where exactly you clicked.
It’s worth
experimenting with this: for example you can
change all the label types by double-clicking on
the chart body, and this gives a way of labelling
the slices of a pie chart with absolute values
rather than percentages (an option surprisingly absent from the ChartWizard menus). If you adjust the
13 If this toolbar doesn’t appear, then select “Toolbars...” from the View menu and check the “Chart” box.
14 In this case, the best combination of clarity and informativeness is
probably to delete the “Ti/H/P” and “Trace” labels, and to rely on the legend
to convey that information.
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ACOM 1010 Introductory IT Skills
Introduction to Excel (Science students)
Lecture 6
colours and fill patterns then bear in mind that you will probably be printing in black and white – but you can
see roughly how the screen colours will appear in grey on the printed page by clicking on the Toolbar’s
Print Preview button. In fact Excel sometimes “chooses” colours that will not print particularly well, and
changing your colours can be the only way to get a clear printed output of your chart (unless you are able
to print in colour).
Inserting a line of best fit
The alterations covered so far in this section are broadly cosmetic – they have little effect on the
information conveyed by the chart. But there are other possible modifications that are more significant, and
an example of this is the insertion of a “Trendline” or line of best fit. Trendlines can only be inserted into
certain types of chart (and obviously not into a pie chart), so move now to
the HAWDAT worksheet in your open spreadsheet, which should contain the
scatter chart you produced earlier. To insert a trendline into a scatter chart,
you first have to select the data. To do this, highlight the chart (by double
clicking on the chart area) and then click in the region of one of the data
points. All of the data points should become highlighted (as in the
illustration here).
When you have the data points in the HAWDAT worksheet highlighted,
select “Trendline” from the Chart menu.15 A dialogue box will appear asking
you what sort of trendline you would like to have on your chart. Select the
appropriate type, and then click on “OK” if that is all you want to include.
However, clicking on the “Options” index tab before clicking on “OK” offers you the useful possibility of
including the equation of the trendline in your chart. Simply check the “Display Equation on Chart” box (and
then click on “OK”). As with other elements of charts, you can edit the appearance of the trendline once
you have inserted it by double-clicking on it while the chart is active, and then changing any of the
attributes that are available from the resulting dialogue box.
Excel also provides two functions for calculating the position of a line of best fit without actually
drawing it. The first of these is “SLOPE”. In the usual way, any formula containing this function should start
with “=SLOPE(”, after which you can click and drag the mouse to select the range of cells that constitute the
y-values of your graph (i.e. those up the vertical axis – the Age data in cells C8 to C24 in the case of
HAWDAT) – you will see that the formula bar reflects the cells you select. Next type a comma, and then
select in the same way the cells which make up the x-values of the graph (i.e. those along the horizontal
axis – in the case of HAWDAT the Distance data in cells B8 to B24). Finally, type a closing bracket and
press Enter. The formula bar should read “=SLOPE(C8:C24,B8:B24)”,16 and the cell in which you typed
the formula should now show the result of the calculation. The INTERCEPT command for working out the
y-coordinate of the point where the best fit line cuts the y-axis has an identical structure to the SLOPE
command, so here the relevant formula for the HAWDAT data is “=INTERCEPT(C8:C24,B8:B24)”.
Changing the 3-D view
One last alteration that can be very useful if you are using three-dimensional charts is changing the 3-D
view. This can be especially useful with 3-D Pie Charts, as sometimes Excel sets these up with the
smallest pie slices appearing at the back of the chart, so you may need to rotate the chart in order to view
all of the data clearly. To alter the 3-D view, highlight the main body of the chart using the left mouse
button and then click on the right mouse button. This will bring up the now familiar shortcut menu, and one
15 If this menu option is “greyed out” and not selectable, then you have not yet managed to highlight the data correctly, so try to
select them again by clicking in the region of one of the data points.
16 Naturally the relevant ranges of cells do not have to be selected with the mouse, and this formula can be just typed in directly
from the keyboard.
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ACOM 1010 Introductory IT Skills
Introduction to Excel (Science students)
Lecture 6
of the options that should be available is “3-D View...”. If no such option is provided on the shortcut menu,
this means that either you have not selected the
main body of the chart or that the chart you are
trying to edit is not three- dimensional. The
Format 3-D View dialogue box enables you to
change the orientation, angle of elevation, and
sometimes (depending on chart type)
perspective of your 3-D chart.
Transferring Excel Charts and Data
into Word
Charts and tables can of course be printed out from Excel directly (select the “Print...” item from the File
menu) and then collated with a paper copy of a wordprocessed document. Alternatively you can copy and
paste charts and ranges of cells from Excel into Word, which is usually preferable because it gives you far
more control over how the charts, cells and text are integrated.
To paste a chart into Word, first make sure that the chart is selected within Excel by clicking on it with
the mouse (and if necessary use the black square selection handles to re-size it before you copy it). Then
select “Copy” from the Edit menu (or from the right mouse button shortcut menu), which will copy the chart
into the Clipboard. You can then minimise the Excel window (or type ALT+Tab in the usual way) and start
up Word (if you haven’t done so already – if you have, just switch directly into Word). Next identify where in
the Word document you wish to insert the chart, place the cursor there by clicking with the mouse and
finally select “Paste” from the Edit menu, when the chart will be inserted as desired.
You should now be able to create charts from the data in your worksheet,
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ACOM 1010 Introductory IT Skills
Introduction to Excel (Science students)
Lecture 6
Appendix 1: Troubleshooting for Formulae
There are various problems that can occur when entering a formula. If you can’t get a formula to work,
check that:
•
•
•
•
You have put an equals sign at the start of the formula
Your typing is correct
You have not entered a name (for an array of cells) which is undefined
If you are using brackets, check that there are the same number of opening and closing brackets
To help sort out what has gone wrong, here are the most common error messages, together with their
meaning.
Error Code
Meaning
#####
This shows that the cell is too narrow to display the error code – make the column
wider.
#DIV/0
The formula is trying to divide by zero. If you can’t see the problem in the formula
itself, ensure that any names by which you divide have a non-zero value (N.B. blank
cells tend to be treated as zero).
#N/A
No value is available. You are unlikely to get this message unless you use facilities
beyond the scope of this booklet and use an Excel function which in the context fails to
Enter a value.
#NAME?
Excel does not recognise a name used in the formula. Check your typing. If this
doesn’t solve the problem, the Define Name dialogue box will show you which names
have been defined.
#NULL!
You specified an intersection of two areas which do not intersect – not a common
error!
#NUM!
There is a problem with a number in a formula.
#REF!
The formula uses a cell reference that is not valid.
#VALUE!
An argument or operand is of the wrong type. For example, you may have included an
integer (e.g. 6) where the formula needs a real number (e.g. 6.1), or attempted to
calculate with a cell containing text.
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Introduction to Excel (Science students)
Lecture 6