Program sffreqreg | Local frequency interpolation. 
[SYNOPSIS]
sffreqreg < in.rsf > out.rsf mask=mask.rsf nw= dw= w0=0. rect=10 niter=100 verb=n
[PARAMETERS]
float   | dw | = |   | 	frequency step 
string  | mask | = |   | 	auxiliary input file name
int     | niter | =100 |   | 	number of inversion iterations 
int     | nw | = |   | 	number of frequencies 
int     | rect | =10 |   | 	smoothing radius 
bool    | verb | =n |  [y/n] | 	verbosity flag 
float   | w0 | =0. |   | 	first frequency 
[DIRECTORY]
user/yliu
