---

Manual Reference Pages  - SMOOTH (1)

---

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 window in 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 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 FFT’d.

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.

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 fee is hereby granted for research purposes, provided that this copyright notice appears in all copies and in all supporting documentation, and that the software is not redistributed for any fee (except for a nominal shipping charge). Anyone wanting to incorporate all or part of this software in a commercial product must obtain a license from the Medical Research Council.

The MRC makes no representations about the suitability of this software for any purpose. It is provided "as is" without express or implied warranty.

THE MRC DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS, IN NO EVENT SHALL THE A.P.U. BE LIABLE FOR ANY SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR 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 THIS SOFTWARE.