NAME

smooth - Data smoothing by convolution with Gaussian window.

CONTENTS

Syntax
Description
Options
Copyright

smooth [options] [file]

Low-pass filter by convolving the input with a unit area Gaussian windowin the time or frequency domain.The transform between domains uses the FFT.

1. length

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.

2. domain

Select algorithm for smoothing.In the time domain ("domain=time") the discrete convolution formula is applieddirectly as a local averaging operation on the input with weights obtainedby time-reversing and shifting a Gaussian window.In the frequency domain ("domain=frequency") the FFT of the whole input ismultiplied by a Gaussian frequency response function (the FFT of theGaussian window), and the result inverse FFT’d.

3. variance, range

The variance of the Gaussian window and itsordinal 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 amountof 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.

4. type

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

Permission to use, copy, modify, and distribute this software without feeis hereby granted for research purposes, provided that this copyrightnotice appears in all copies and in all supporting documentation, and thatthe software is not redistributed for any fee (except for a nominalshipping charge). Anyone wanting to incorporate all or part of thissoftware in a commercial product must obtain a license from the MedicalResearch Council.

The MRC makes no representations about the suitability of thissoftware for any purpose. It is provided "as is" without express orimplied warranty.

THE MRC DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE, INCLUDINGALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS, IN NO EVENT SHALLTHE A.P.U. BE LIABLE FOR ANY SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGESOR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS,WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION,ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THISSOFTWARE.