TOPICS

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TOPICS

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A. Arrays

B. Common Array Functions

C. Polymorphism

D. Auto-Indexing

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E. Clusters

F. Type Definitions

G. Plotting Data

– Charts

and Graphs

Data Structures

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A. Arrays

1D and 2D Arrays

Creating an Array Control and Constant

Initializing Arrays

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Arrays

An array:
• Is a collection of data elements

that are of same type.

• Has one or more dimensions.
• Contains up to (2

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)

–1 elements

per dimension, memory
permitting.

• Accesses elements by its index.

Note: The first element is index 0.

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1D array

One row of 10-elements

1.2 3.2

8.2 8.0

4.8 5.1

6.0 1.0

2.5 1.7

0 1 2 3 4 5 6 7 8 9

2D array

Five-row by seven-column table of
35 elements

0 1 2 3 4 5 6

0

1
2
3
4

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Arrays

– 1D and 2D Examples

Index

numbers

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Why Use Arrays?

Use arrays when you work with a collection of
similar data and when you perform repetitive
computations.

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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.

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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.

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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.

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Viewing Arrays on the Front Panel

The element selected in the index display always
refers to the element shown in the upper-left
corner of the element display.

First
element at
index 1

Second
element at
index 2

The element at
index 0 is not shown
because element 1
is selected in the
index display.

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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.

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B. Common Array Functions

Array Size

Initialize Array

Array Subset

Build Array

Index Array

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Common Array Functions

• Array Size
• Initialize Array
• Array Subset
• Build Array
• Index Array

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Array Size

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Initialize Array

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Array Subset

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Build Array

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Index Array

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C. Polymorphism

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Polymorphism

Functions are polymorphic to varying degrees:

• 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.

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Polymorphism - The ability of VIs and
functions to automatically adapt to accept
input data of different data types

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Arithmetic Functions Are
Polymorphic

Combination

Result

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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

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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.

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Wire becomes thicker

Wire remains the same size

Auto-Indexing Disabled

Auto-Indexing Enabled

Only one value (last
iteration) is passed out
of the loop

1D Array

0 1 2 3 4 5

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Auto-Indexing with a Conditional
Tunnel

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Right-click on a tunnel and
select Tunnel
Mode»Conditional.

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• Inner loop creates column elements (creates single rows).
• Outer loop stacks column elements into a 2D array.

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1D Array

0 1 2 3 4 5

2D Array

Creating 2D Arrays

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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.

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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.

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DEMONSTRATION

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.

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E. Clusters

Reasons To Use Clusters

Clusters vs. Arrays

Creating a Cluster Control and Constant

Ordering Items and Resizing Clusters

Disassembling and Modifying Clusters

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Clusters

• Clusters group data elements of mixed types.
• Clusters are similar to a record or a

struct

in

text-based programming languages.

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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.

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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.

• 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.

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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.

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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.

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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.

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Cluster Order

• Cluster elements have a

logical order unrelated to
their position in the shell.

• You can view and modify

the
cluster order by right-
clicking
the cluster border and
selecting Reorder
Controls
In Cluster.

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Disassembling a Cluster

• Use the Unbundle By Name function whenever

possible.

• Use Unbundle function when some or all cluster

elements are unnamed.

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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.

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You
must
wire the
input
cluster
terminal.

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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.

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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.

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DEMONSTRATION

Demonstration:
Clusters

Create clusters, reorder clusters, and use the
cluster functions to assemble and disassemble
elements.

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DISCUSSION

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)?

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F. Type Definitions

Type Definitions and Custom Data Types

Creating and Identifying Type Definitions

Controls

Strict Type Definitions

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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.

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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.

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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.

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DEMONSTRATION

Demonstration:
Type Definition

Create and modify a type-defined cluster control.
Use the type definition in a calling VI and a subVI.

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Other Control Options

You can save a custom
control as:
• Control
• Type Definition
• Strict Type Definition

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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.

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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.

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.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

Type Def

•

Connection between the
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

Strict Type Def

•

Connection between
saved file and all
instances

•

Forces everything about
an instance to be
identical to the strict type
definition, except:

•label
•description
•default value

*.ctl

*.ctl

*.ctl

DISCUSSION

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?

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G. Plotting Data

– Charts and

Graphs

Waveform Chart

Waveform Graph

XY Graph

Multiplot Charts and Graphs

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Waveform Chart

• Waveform chart

is a special type
of numeric
indicator.

• Waveform

charts display
single or
multiple plots.

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Waveform Chart Properties

Extensive plot
customization lets
you:
• Show or hide

legends.

• Change color and

line styles.

• Change

interpolation
styles.

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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.

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• 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.

Chart Update Modes

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Waveform Graph

• Is a graphical display

of data.

• Displays one or more

plots of evenly sampled
measurements.

• Is used to plot pre-

generated arrays of data.

• Can display plots with any number of data points.

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Charts vs. Graphs

– Single Plot

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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.

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Charts vs. Graphs

– Multi-plot

and XY Graph

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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.

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Homework: Data Structures

Practice creating and using:
• arrays
• clusters
• custom controls and type definitions.
The instructions are provided on the website.

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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.