SUFILTER - applies a zero-phase, sine-squared tapered filter

sufilter <stdin >stdout [optional parameters]

Required parameters:
if dt is not set in header, then dt is mandatory

Optional parameters:
f=f1,f2,... array of filter frequencies(HZ)
amps=a1,a2,... array of filter amplitudes
dt = (from header) time sampling interval (sec)

Defaults:f=.10*(nyquist),.15*(nyquist),.45*(nyquist),.50*(nyquist)
(nyquist calculated internally)
amps=0.,1.,...,1.,0. trapezoid-like bandpass filter

Examples of filters:
Bandpass: sufilter <data f=10,20,40,50 | ...
Bandreject: sufilter <data f=10,20,30,40 amps=1.,0.,0.,1. | ..
Lowpass: sufilter <data f=10,20,40,50 amps=1.,1.,0.,0. | ...
Highpass: sufilter <data f=10,20,40,50 amps=0.,0.,1.,1. | ...
Notch: sufilter <data f=10,12.5,35,50,60 amps=1.,.5,0.,.5,1. |..

Credits:
CWP: John Stockwell, Jack Cohen

Possible optimization: Do assignments instead of crmuls where
filter is 0.0.

Trace header fields accessed: ns, dt