# Signal Correlation (2D Auto-Correlation) (G Dataflow)

Computes the two-dimensional auto correlation of a sequence.

## X

The input sequence.

This input can be a 2D array of double-precision, floating-point numbers or a 2D array of complex double-precision, floating-point numbers.

## error in

Error conditions that occur before this node runs.

The node responds to this input according to standard error behavior.

Standard Error Behavior

Many nodes provide an error in input and an error out output so that the node can respond to and communicate errors that occur while code is running. The value of error in specifies whether an error occurred before the node runs. Most nodes respond to values of error in in a standard, predictable way.

error in does not contain an error error in contains an error
If no error occurred before the node runs, the node begins execution normally.

If no error occurs while the node runs, it returns no error. If an error does occur while the node runs, it returns that error information as error out.

If an error occurred before the node runs, the node does not execute. Instead, it returns the error in value as error out.

Default: No error

## RXX

The auto correlation of the input sequence.

The output can return a 2D array of double-precision, floating-point numbers or a 2D array of complex double-precision, floating-point numbers.

## error out

Error information.

The node produces this output according to standard error behavior.

Standard Error Behavior

Many nodes provide an error in input and an error out output so that the node can respond to and communicate errors that occur while code is running. The value of error in specifies whether an error occurred before the node runs. Most nodes respond to values of error in in a standard, predictable way.

error in does not contain an error error in contains an error
If no error occurred before the node runs, the node begins execution normally.

If no error occurs while the node runs, it returns no error. If an error does occur while the node runs, it returns that error information as error out.

If an error occurred before the node runs, the node does not execute. Instead, it returns the error in value as error out.

## Algorithm for Calculating the 2D Auto-Correlation

This node computes two-dimensional auto-correlation using the following equation:

$y\left(i,j\right)=\sum _{m=0}^{M-1}\sum _{n=0}^{N-1}{x}^{*}\left(m,n\right)\cdot x\left(m+i,n+j\right)$

for i = -(M-1), ..., -1, 0, 1, ... , (M-1) and j = -(N-1), ..., -1, 0, 1, ... , (N-1)

where M is the number of rows of matrix X and N is the number of columns of matrix X. The indexed elements of X that lie outside its range are equal to zero, as shown in the following relationship:

$x\left(m,n\right)=0,\text{}m<0\text{}\mathrm{or}\text{}m\ge M\text{}\mathrm{or}\text{}n<0\text{}\mathrm{or}\text{}n\ge N$

Where This Node Can Run:

Desktop OS: Windows

FPGA: Not supported

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