Synopsis
		sfdsmooth < in.rsf > out.rsf ider=0 repeat=1 nderiv=6 rect#=(1,1,...)

Parameters
		int ider=0 direction of the derivative (0 means no derivative)   int nderiv=6 derivative filter accuracy   int rect#=(1,1,...) smoothing radius on #-th axis   int repeat=1 repeat smoothing several times