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Median Filter (G Dataflow)

Last Modified: January 12, 2018

Applies a median filter of rank to a signal.

Rank is right rank if right rank is greater than zero. Rank is left rank if right rank is less than zero.

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reset

A Boolean that specifies the initialization of the internal state of the node.

True Initializes the internal state to zero.
False Initializes the internal state to the final state from the previous call of this node.

This node automatically initializes the internal state to zero on the first call and runs continuously until this input is True.

This input is available only if you wire a double-precision, floating-point number to signal.

Default: False

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signal

Input signal to filter.

This input accepts the following data types:

  • Double-precision, floating-point number
  • 1D array of double-precision, floating-point numbers
  • Waveform
  • 1D array of waveforms

If you wire an array or waveform to signal, the number of elements, n, in signal must be greater than right rank. If the number of elements in signal is less than or equal to right rank, the node sets filtered signal to an empty array and returns an error.

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left rank

Number of elements used to compute the median filter to the left side.

left rank must be greater than or equal to 0.

Default: 2

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right rank

Number of elements used to compute the median filter to the right side.

If right rank is less than 0, the node assumes right rank is equal to left rank. right rank must be less than the number of elements in signal.

Default: -1

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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

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filtered signal

Filtered signal.

This output can return the following data types:

  • Double-precision, floating-point number
  • 1D array of double-precision, floating-point numbers
  • Waveform
  • 1D array of waveforms
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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 Definition

This node obtains the elements of filtered signal using the following equation.

Y i = Median ( J i ) for i = 0 , 1 , 2 , ... , n 1

where

  • Y is filtered signal
  • n is the number of elements in signal
  • Ji is a subset of signal centered about the ith element of signal
  • The indexed elements outside the range of signal equal zero.

The following equation describes Ji.

J i = { X i r l , X i r l + 1 , K , X i 1 , X i , X i + 1 , K , X i + r r 1 , X i + r r }

where rl is the filter left rank, and rr is the filter right rank.

The following illustration shows the computation of Yi.

Where This Node Can Run:

Desktop OS: Windows

FPGA: Not supported

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


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