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bwfilterf
Butterworth filter for a vector/scalar field

Description
FF = bwfilterf(F,FSIZE,ORDER) applies a lowpass Butterworth filter 
to the vector/scalar field F  with a cutoff size FSIZE (in grid units) 
and order ORDER.  F must be a square vector or scalar field; if it is 
not square, bwfilterf first extracts the the central square of F (see 
extractf). Typical values for FSIZE are around 1, and typical values 
for ORDER are in the range 2-10. 
 
FF = bwfilterf(F,FSIZE,ORDER,OPT), where OPT is a string that may 
contain one or several substrings: 
  'low', 'high':   specifies a lowpass (by default) or highpass filter 
  't':             truncates the borders of width FSIZE, which are 
                   affected by the filtering. 
 
If no output argument, the result is displayed by showvec or showscal. 
 
bwfilterf first Fourier transforms the field(s), low/high-pass 
filters and inverse Fourier transformsF. 
 
Note: A highpass filter of order ORDER is equivalent to a lowpass 
filter of order -ORDER. 
 
Example:  showvec(bwfilterf(loadset,3,8)); 
 
F. Moisy 
Revision: 1.10,  Date: 2005/10/09 
 
See Also
filterf, addnoisef, truncf, extractf. 

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