Computes the auto-correlation of a signal.
The normalization method to use to compute the auto correlation of the input signal.
This input is available only if x is a waveform or an array.
Name | Description |
---|---|
none |
Does not apply normalization. |
unbiased |
Applies unbiased normalization. |
biased |
Applies biased normalization. |
Default: none
Length of each set of x-values. This node computes each set of values separately.
sample length x must be greater than 0.
This input is available only if x is a double-precision, floating-point number.
Default: 100
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.
Default: No error
A Boolean that specifies whether to use the data points before the current block to compute the auto-correlation.
True | Uses the data points before the current block to compute the auto-correlation. |
False | Does not use the data points before the current block to compute the auto-correlation. |
This input is available only if x is a double-precision, floating-point number.
Default: True
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.
The auto-correlation Rxx(t) of a function x(t) is defined as
where the symbol denotes correlation.
For the discrete implementation of this node, let Y represent a sequence whose indexing can be negative, let N be the number of elements in the input sequence x, and assume that the indexed elements of x that lie outside its range are equal to zero, as shown in the following relationship:
Then this node obtains the elements of Y using the following formula:
for
The elements of the output sequence Rxx are related to the elements in the sequence Y by
for
Notice that the number of elements in the output sequence Rxx is . Because you cannot use negative numbers to index arrays, the corresponding correlation value at t = 0 is the Nth element of the output sequence Rxx. Therefore, Rxx represents the correlation values that this node shifts N times in indexing.
This node applies unbiased normalization as follows:
for j = -(N-1), -(N-2), ..., -1, 0, 1, ..., (N-2), (N-1), and
for i = 0, 1, 2, ..., 2N-2
This node applies biased normalization as follows:
for j = -(N-1), -(N-2), ..., -1, 0, 1, ..., (N-2), (N-1), and
for i = 0, 1, 2, ..., 2N-2
Where This Node Can Run:
Desktop OS: Windows
FPGA: Not supported
Web Server: Not supported in VIs that run in a web application