TOPICS
0
ni.com/training
Data Structures
TOPICS
A.
B.
C.
D.
1
Arrays
Common Array Functions
Polymorphism
Auto-Indexing
E. Clusters
F. Type Definitions
G. Plotting Data – Charts
and Graphs
ni.com/training
A. Arrays
1D and 2D Arrays
Creating an Array Control and Constant
Initializing Arrays
2
ni.com/training
Arrays
An array:
• Is a collection of data elements
that are of same type.
• Has one or more dimensions.
• Contains up to (231)–1 elements
per dimension, memory
permitting.
• Accesses elements by its index.
Note: The first element is index 0.
3
ni.com/training
Arrays – 1D and 2D Examples
1D array
One row of 10-elements
0
1
2
3
4
5
6
7
8
9
1.2 3.2 8.2 8.0 4.8 5.1 6.0 1.0 2.5 1.7
2D array
Five-row by seven-column table of
35 elements
0
1
2
3
4
5
Index
numbers
6
0
1
2
3
4
4
ni.com/training
Why Use Arrays?
Use arrays when you work with a collection of
similar data and when you perform repetitive
computations.
5
ni.com/training
Creating an Array Control
For a new array:
1. Select an Array control from
the Controls palette on the
front panel.
2. Place a data object, such as
a numeric control, into the
array shell.
3. Add more dimensions, if
necessary, by resizing the index display.
From a block diagram terminal or wire:
1. Right-click the object and select Create»Control or
Create»Indicator.
6
ni.com/training
Creating an Array Constant
For a new array:
1. Select Array Constant from the
Functions palette on the block
diagram.
2. Place a constant, such as a numeric,
into the array shell.
3. Add more dimensions, if necessary, by
resizing the index.
From a block diagram terminal or wire:
1. Right-click and select
Create»Constant.
7
ni.com/training
2D Arrays
• 2D arrays:
− Store elements in a grid.
− Require a row index and a column index to locate
an element, both of which are zero-based.
• Create a multidimensional array on the front
panel by right-clicking the index display and
selecting Add Dimension from the shortcut
menu, or:
• Resize the index display until you have as many
dimensions as you want.
8
ni.com/training
Viewing Arrays on the Front Panel
The element at
index 0 is not shown
because element 1
is selected in the
index display.
First
element at
index 1
Second
element at
index 2
The element selected in the index display always
refers to the element shown in the upper-left
corner of the element display.
9
ni.com/training
Initializing Arrays
• You can initialize an array or leave it uninitialized.
• For initialized arrays, you define the number of
elements in each dimension and the contents of
each element.
• Uninitialized arrays have dimension but no
elements.
10
ni.com/training
B. Common Array Functions
Array Size
Initialize Array
Array Subset
Build Array
Index Array
11
ni.com/training
Common Array Functions
•
•
•
•
•
12
Array Size
Initialize Array
Array Subset
Build Array
Index Array
ni.com/training
Array Size
13
ni.com/training
Initialize Array
14
ni.com/training
Array Subset
15
ni.com/training
Build Array
16
ni.com/training
Index Array
17
ni.com/training
C. Polymorphism
18
ni.com/training
Polymorphism
Polymorphism - The ability of VIs and
functions to automatically adapt to accept
input data of different data types
Functions are polymorphic to varying degrees:
•
•
•
•
19
None, some, or all of their inputs can be polymorphic.
Some accept numeric or Boolean values.
Some accept numeric or strings.
Some accept scalars, numeric arrays, or clusters of
numerics.
ni.com/training
Arithmetic Functions Are
Polymorphic
Combination
20
Result
ni.com/training
D. Auto-Indexing
Use in For Loops and While Loops
Auto-Indexing with a Conditional Terminal
Creating 2D Arrays
Auto-Indexing Input to a Loop
21
ni.com/training
Auto-Indexing
• Allows loops to
accumulate arrays at their
boundaries.
• Is the default behavior for
For Loops.
• Is disabled by default for
While Loops.
• Is enabled/disabled by
right-clicking on a tunnel.
• Produces arrays that are
always equal in size to the
number of iterations of the
loop.
22
Auto-Indexing Enabled
Wire becomes thicker
1D Array
0 1
2
3 4
5
Auto-Indexing Disabled
Wire remains the same size
Only one value (last
iteration) is passed out
of the loop
ni.com/training
Auto-Indexing with a Conditional
Tunnel
Right-click on a tunnel and
select Tunnel
Mode»Conditional.
23
ni.com/training
Creating 2D Arrays
1D Array
0 1
2
3 4
2D Array
5
• Inner loop creates column elements (creates single rows).
• Outer loop stacks column elements into a 2D array.
24
ni.com/training
Auto-Indexing Input
If the iteration count terminal is wired and arrays of
different sizes are wired to auto-indexed tunnels, the
actual number of iterations becomes the smallest of
the choices.
25
ni.com/training
25
Auto-Indexing Input
Use an auto-indexing input array to perform
calculations on each element in an array.
•
Wire an array to an auto-indexing tunnel on a For Loop.
•
You do not need to wire the count (N) terminal.
−
The For Loop executes
the number of times
equal to the
number of
elements in the array.
−
The Run button is not broken.
26
ni.com/training
26
Concept:
Polymorphism and Manipulating Arrays
Build a VI where an array and a scalar are added
in two ways:
– Polymorphic Add of array + scalar
– Auto-indexed array elements added to scalar
and verify that the results are the same.
DEMONSTRATION
E. Clusters
Reasons To Use Clusters
Clusters vs. Arrays
Creating a Cluster Control and Constant
Ordering Items and Resizing Clusters
Disassembling and Modifying Clusters
28
ni.com/training
Clusters
• Clusters group data elements of mixed types.
• Clusters are similar to a record or a struct in
text-based programming languages.
29
ni.com/training
29
Why Use Clusters?
• Keep data organized.
− Logically group related data values together.
− Improve diagram readability by eliminating wire
clutter.
• Reduce the number of connector pane terminals.
30
ni.com/training
Clusters vs. Arrays
• A cluster has a fixed
number of elements.
• One cluster can contain
mixed data types.
• A cluster can contain
another cluster directly.
• A cluster can be a control,
an indicator, or a constant.
− All cluster elements have
to be controls, indicators,
or constants.
31
• An array can vary in size.
• One array contains only
one data type.
• An array cannot contain
another array directly.
• An array can be a control,
an indicator, or a constant.
− All array elements have to
be controls, indicators, or
constants.
ni.com/training
31
Create a Cluster Control
For a new cluster:
1. On the front panel, select Cluster
from the Controls palette.
2. Place a data object into the
cluster shell.
3. Place additional data objects,
if necessary, into the shell.
From block diagram terminal or wire:
1. Right-click and select Create»Control or
Create»Indicator.
32
ni.com/training
32
Create a Cluster Constant
For a new cluster:
1. On the block diagram, select
Cluster Constant from the
Functions palette.
2. Place a constant into the cluster
shell.
3. Place additional data objects, if
necessary, into the cluster shell.
From block diagram terminal or
wire:
1. Right-click and select
Create»Constant.
33
ni.com/training
33
Autosizing Clusters
• Autosizing helps you
arrange elements in
clusters.
• NI recommends the
following:
− Arrange cluster elements
vertically.
− Arrange elements
compactly.
− Arranges elements in
their preferred order.
34
ni.com/training
Cluster Order
• Cluster elements have a
logical order unrelated to
their position in the shell.
• You can view and modify
the
cluster order by rightclicking
the cluster border and
selecting Reorder
Controls
In Cluster.
35
ni.com/training
Disassembling a Cluster
• Use the Unbundle By Name function whenever
possible.
• Use Unbundle function when some or all cluster
elements are unnamed.
36
ni.com/training
Modifying a Cluster
• Use Bundle By Name whenever possible to
access elements in a cluster.
• Use Bundle when some or all cluster elements
are unnamed.
You
must
wire the
input
cluster
terminal.
37
ni.com/training
Creating a Cluster on the Diagram
• Use the Bundle function to programmatically create
a cluster on a block diagram.
• If the elements that are bundled have labels, you
can access them using the Unbundle By Name
function. Otherwise use the Unbundle function.
38
ni.com/training
Error Clusters
• LabVIEW uses error clusters to pass error information.
• An error cluster contains the following elements:
− status—Boolean value that reports True if an error occurs.
− code—32-bit signed integer that identifies the error.
− source—String that identifies where the error occurred.
39
ni.com/training
Demonstration:
Clusters
Create clusters, reorder clusters, and use the
cluster functions to assemble and disassemble
elements.
DEMONSTRATION
Group Exercise
Concept: Bundle and Unbundle
Functions
• What happens to VIs using your cluster if you
reorder cluster elements:
– if you use Bundle By Name and Unbundle By Name
in your VIs?
– if you use Bundle and Unbundle in your VIs?
DISCUSSION
Group Exercise
Concept: Editing Cluster Elements
You perform some operations on a cluster, e.g.
replace one element as in the picture above. What
happens if you add a cluster element to Output
cluster (by editing the front panel indicator)?
DISCUSSION
F. Type Definitions
Type Definitions and Custom Data Types
Creating and Identifying Type Definitions
Controls
Strict Type Definitions
43
ni.com/training
Type Definition (Type Def)
• A type definition is a master copy of a custom
data type (control, indicator, or constant).
− A custom data type is saved in a .ctl file.
− Instances of a type def are linked to the .ctl file.
• Instances can be controls, indicators, or
constants.
• When the type def changes, instances
automatically update.
− Changes include data type changes, elements
added, elements removed, and adding items to an
enum.
44
ni.com/training
Creating a Type Definition (Type Def)
1. Right-click a control, indicator or constant and select
Make Typedef.
1. Right-click the object again and select Open Type Def.
2. Edit control, if needed.
3. Save control as a .ctl file.
45
ni.com/training
Identifying Type Definitions (Type
Def)
• Look for a glyph marking the upper left corner of
terminals and constants.
• Hover cursor over glyph to view tip strip.
• View Context Help while hovering cursor over
terminal or constant.
46
ni.com/training
Demonstration:
Type Definition
Create and modify a type-defined cluster control.
Use the type definition in a calling VI and a subVI.
DEMONSTRATION
Other Control Options
You can save a custom
control as:
• Control
• Type Definition
• Strict Type Definition
48
ni.com/training
48
Control
• Instances are not linked to a.ctl file.
• Each instance is an independent copy of the
control.
• Used to create controls
that behave like existing
controls but look different.
49
ni.com/training
Strict Type Definition
• Strict type definitions are similar to a type definition in
that:
− All instances link to .ctl file.
− When attributes or data types change, all instances
update.
• Examples: Changing a knob to a dial, a round LED to
a square LED, or a double to an integer.
• Strict type definitions enforce every aspect of a
instance except label, description, and default value.
• Use strict type definitions to ensure all front panel
instances have the same appearance.
50
ni.com/training
50
.ctl File Options Summary
Control
•
•
No connection
between the one
you saved and the
instance in the VI
Update to the file
will not update
any instances
*.ctl
Type Def
Strict Type Def
•
Connection between the
saved file and all
instances
•
Connection between
saved file and all
instances
•
Forces the data type of
each instance to be
identical (clusters, enum)
•
•
Changes made to file will
populate throughout each
instance
Forces everything about
an instance to be
identical to the strict type
definition, except:
•label
•description
•default value
*.ctl
*.ctl
ni.com/training
Group Exercise
Concept: Type Definitions
If your cluster is saved as a type definition and you
use this cluster in five places in your VIs, how
many instances of the cluster would need to be
updated to add more cluster elements?
DISCUSSION
G. Plotting Data – Charts and
Graphs
Waveform Chart
Waveform Graph
XY Graph
Multiplot Charts and Graphs
53
ni.com/training
Waveform Chart
• Waveform chart
is a special type
of numeric
indicator.
• Waveform
charts display
single or
multiple plots.
54
ni.com/training
Waveform Chart Properties
Extensive plot
customization lets
you:
• Show or hide
legends.
• Change color and
line styles.
• Change
interpolation
styles.
55
ni.com/training
Waveform Chart – Visible Items
Charts also have elements that can be made visible
on the front panel so the user can change chart
appearance when
the application
is running.
These are e.g.:
• Plot Legend
• Scale Legend
• Graph Palette.
ni.com/training
Chart Update Modes
• Right-click the chart and select Advanced»Update Mode
from the shortcut menu.
• Strip chart is the default update mode.
• Scope chart and sweep chart modes display plots
significantly faster than the strip chart mode.
ni.com/training
Waveform Graph
• Is a graphical display
of data.
• Displays one or more
plots of evenly sampled
measurements.
• Is used to plot pregenerated arrays of data.
• Can display plots with any number of data points.
58
ni.com/training
Charts vs. Graphs – Single Plot
59
ni.com/training
XY Graph
• Is a graphical display of data.
• Can display plots such as
circular shapes or
waveforms with
a varying time base.
• Data points may be evenly
sampled or not.
• Is used to plot pre-generated arrays of data.
• Can display plots with any number of data points.
60
ni.com/training
Charts vs. Graphs – Multi-plot
and XY Graph
61
ni.com/training
Plotting Data
Use the Context Help
window to determine
how to wire data
(including multi-plot data)
to Waveform Graphs,
Waveform Charts and
XY Graphs.
62
ni.com/training
Homework: Data Structures
Practice creating and using:
• arrays
• clusters
• custom controls and type definitions.
The instructions are provided on the website.
ni.com/training
Homework: Lotto
Utilize your knowlegde about arrays,
For and While loops, and Case Structures
to implement a ”Pick 6” lottery.
The instructions are provided on the website.
ni.com/training