Manual Reference Pages - SMOOTH (1)
smooth - Data smoothing by convolution with Gaussian window.
smooth [options] [file]
Low-pass filter by convolving the input with a unit area Gaussian window in the time or frequency domain. The transform between domains uses the FFT.
The amount of input to smooth in time units (ms or s) or samples (no units). Time units are converted to samples using the given samplerate option. The string "max" is recognised as the remainder of input.
Select algorithm for smoothing. In the time domain ("domain=time") the discrete convolution formula is applied directly as a local averaging operation on the input with weights obtained by time-reversing and shifting a Gaussian window. In the frequency domain ("domain=frequency") the FFT of the whole input is multiplied by a Gaussian frequency response function (the FFT of the Gaussian window), and the result inverse FFTd.
3. variance, range
The variance of the Gaussian window and its ordinal range in standard deviations either side of the mode. The window is assumed to be zero for all time outside the specified range. These parameters control the size of the window and consequently the amount of smoothing. The larger the variance, the more smoothing. The size of the window is given by:
[ 2 * range * sqrt( variance ) ] samples + 1 sample
The variance can be given with time units (ms or s) or samples (no units). Time units are converted to samples using the given samplerate option.
The input and output data type. Recognised types are "short" and "float".
options gauss filt1 conv
Copyright (c) Applied Psychology Unit, Medical Research Council, 1995
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|SunOS 5.6||SMOOTH (1)||1 September 1993|