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Index Array (Clock-Driven Logic)

Last Modified: September 13, 2017

Returns the value stored in an array at a specified index.

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array

An n-dimensional array of any type.

If array is an empty array, element returns the default value of the defined data type for the array.

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index

A number that refers to a location within the input array.

This node automatically provides an index input for each dimension of the array.

Behavior for Out of Range Values

If index for any dimension is less than zero or greater than the length of array in that dimension, this node returns the default value of the defined data type for the array.

Relationship between index Inputs and array Dimensions

For multidimensional arrays, index inputs correspond to row-major order. Thus, the first index corresponds last dimension of the array input, and the last index corresponds to the first dimension of the array input. The following table shows the relationship between four index inputs and the dimensions of a 4D array input.

index Order Corresponding Dimension in array Input index Name
1 4th volume index
2 3rd page index
3 2nd row index
4 1st column index

Unwired Index Inputs

Unwired index inputs allow you to retrieve a subarray of the array rather than a single element. For example, to retrieve column 1 of a 2D array, specify 1 in the column index and leave the row index unwired.

When all index inputs are unwired, the retrieved subarray contains one less dimension than array.

Relationship between index and Multiple element or subarray Outputs

If you expand the node to show more than one element or subarray output, the node provides a set of index inputs for each output. The values you wire to a set of index inputs determine the value of the corresponding output. However, if you do not wire values to a set of index inputs, the corresponding element or subarray output returns the element or subarray that follows the previous element or subarray output in the original array. Refer to the Examples tab for an illustration of this relationship.

Default: 0

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element

The scalar element or subarray stored in array at the specified index.

Resizing Behavior

When you wire an array to this node, the node resizes automatically to display index inputs for each dimension in the array you wire to array. You also can add additional element or subarray outputs by resizing the node. The node provides index inputs for each output.

Accessing a Subarray by Disabling Indexing along a Dimension

You can disable indexing along a dimension by leaving the corresponding index input unwired. By default, the first dimension has indexing enabled, with the others disabled. You can wire a constant or control to the index inputs that you want enabled.

For example, if you want to index a row in a 2D array, the first index input is enabled and the second index input is disabled. If you want to index that same 2D array also by column, you can resize the node to show another set of input terminals. This next set of inputs has its own corresponding element output. By default, if you do not wire any index input terminals, the first element indexes row 0, the second element indexes row 1, and so on.

Where This Node Can Run:

Desktop OS: none

FPGA: All devices

Web Server: Not supported in VIs that run in a web application


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