# Copyright (c) 2002 Peter Guntert. All rights reserved.
## 7MACROS: suppress - suppress signals with zero frequency
##
## Usage: suppress [<weighting> [<n>]]
##
## suppress is a standard macro that suppresses signals with zero frequency
## (e.g. the water line) by subtracting smoothed time-domain data from
## the original time-domain data. To obtain the smoothed data s'(k) the 
## a moving average over the original data s(k) is calculated:
##
##            f(-n) s(k-n) + ... + f(0) s(k) + ... + f(n) s(k+n)
##    s'(k) = --------------------------------------------------.
##                   f(-n) + ... +    f(0)   + ... + f(n)
##
## The default value for n is the number of data points in the active di-
## mension divided by 20. The following weighting functions are available:
##
## weighting   f(k)                remarks
## ---------   -----------------   --------------------------
## cos         cos(pi/(2*n+2)*k)   cosine weighting (default)
## gauss       exp(-4*(k/n)**2)    Gaussian weighting
## equal       1.0                 equal weights
##
## See also: smooth

parameter type nsmooth

if (nparam.gt.2) error "*** Error: Illegal number of parameters."
if (.not.def('type')) type := cos
if (.not.def('nsmooth')) nsmooth = n/20
type := '$type'

if (type.eq.'cos') then
  smooth nsmooth cos(0.5*pi/(nsmooth+1)*k) extrapolate=nsmooth+3 subtract
else if (type.eq.'gauss') then
  smooth nsmooth exp(-4.0*(k/nsmooth)**2) extrapolate=nsmooth+3 subtract
else if (type.eq.'equal') then
  smooth nsmooth 1.0 extrapolate=nsmooth+3 subtract
else
  error "*** Error: Illegal weighting function \"$type\"."
end if