view man/man1/smooth.1 @ 0:5242703e91d3 tip

Initial checkin for AIM92 aimR8.2 (last updated May 1997).

.TH SMOOTH 1 "1 September 1993"

.SH NAME
smooth  \- Data smoothing by convolution with Gaussian window.

.SH SYNTAX 
smooth [options] [file]

.SH DESCRIPTION
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.


.SH OPTIONS

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:

.nf
	[ 2 * range * sqrt( variance ) ] samples   +  1 sample
.fi

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".

.SH "SEE ALSO"
options gauss filt1 conv

.SH COPYRIGHT
.LP
Copyright (c) Applied Psychology Unit, Medical Research Council, 1995
.LP
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.
.LP
The MRC makes no representations about the suitability of this 
software for any purpose.  It is provided "as is" without express or 
implied warranty.
.LP
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.