tomwalters@0: .TH SMOOTH 1 "1 September 1993"
tomwalters@0: 
tomwalters@0: .SH NAME
tomwalters@0: smooth  \- Data smoothing by convolution with Gaussian window.
tomwalters@0: 
tomwalters@0: .SH SYNTAX 
tomwalters@0: smooth [options] [file]
tomwalters@0: 
tomwalters@0: .SH DESCRIPTION
tomwalters@0: Low-pass filter by convolving the input with a unit area Gaussian window
tomwalters@0: in the time or frequency domain.
tomwalters@0: The transform between domains uses the FFT.
tomwalters@0: 
tomwalters@0: 
tomwalters@0: .SH OPTIONS
tomwalters@0: 
tomwalters@0: 1. length
tomwalters@0: 
tomwalters@0: The amount of input to smooth in time units (ms or s) or samples (no units).
tomwalters@0: Time units are converted to samples using the given `samplerate' option.
tomwalters@0: The string "max" is recognised as the remainder of input.
tomwalters@0: 
tomwalters@0: 2. domain
tomwalters@0: 
tomwalters@0: Select algorithm for smoothing.
tomwalters@0: In the time domain ("domain=time") the discrete convolution formula is applied
tomwalters@0: directly as a local averaging operation on the input with weights obtained
tomwalters@0: by time-reversing and shifting a Gaussian window.
tomwalters@0: In the frequency domain ("domain=frequency") the FFT of the whole input is
tomwalters@0: multiplied by a Gaussian frequency response function (the FFT of the
tomwalters@0: Gaussian window), and the result inverse FFT'd.
tomwalters@0: 
tomwalters@0: 3. variance, range
tomwalters@0: 
tomwalters@0: The variance of the Gaussian window and its
tomwalters@0: ordinal range in standard deviations either side of the mode.
tomwalters@0: The window is assumed to be zero for all time outside the specified range.
tomwalters@0: These parameters control the size of the window and consequently the amount
tomwalters@0: of smoothing. The larger the variance, the more smoothing.
tomwalters@0: The size of the window is given by:
tomwalters@0: 
tomwalters@0: .nf
tomwalters@0: 	[ 2 * range * sqrt( variance ) ] samples   +  1 sample
tomwalters@0: .fi
tomwalters@0: 
tomwalters@0: The variance can be given with time units (ms or s) or samples (no units).
tomwalters@0: Time units are converted to samples using the given `samplerate' option.
tomwalters@0: 
tomwalters@0: 4. type
tomwalters@0: 
tomwalters@0: The input and output data type. Recognised types are "short" and "float".
tomwalters@0: 
tomwalters@0: .SH "SEE ALSO"
tomwalters@0: options gauss filt1 conv
tomwalters@0: 
tomwalters@0: .SH COPYRIGHT
tomwalters@0: .LP
tomwalters@0: Copyright (c) Applied Psychology Unit, Medical Research Council, 1995
tomwalters@0: .LP
tomwalters@0: Permission to use, copy, modify, and distribute this software without fee 
tomwalters@0: is hereby granted for research purposes, provided that this copyright 
tomwalters@0: notice appears in all copies and in all supporting documentation, and that 
tomwalters@0: the software is not redistributed for any fee (except for a nominal 
tomwalters@0: shipping charge). Anyone wanting to incorporate all or part of this 
tomwalters@0: software in a commercial product must obtain a license from the Medical 
tomwalters@0: Research Council.
tomwalters@0: .LP
tomwalters@0: The MRC makes no representations about the suitability of this 
tomwalters@0: software for any purpose.  It is provided "as is" without express or 
tomwalters@0: implied warranty.
tomwalters@0: .LP
tomwalters@0: THE MRC DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE, INCLUDING 
tomwalters@0: ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS, IN NO EVENT SHALL 
tomwalters@0: THE A.P.U. BE LIABLE FOR ANY SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES 
tomwalters@0: OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, 
tomwalters@0: WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, 
tomwalters@0: ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS 
tomwalters@0: SOFTWARE.
tomwalters@0: