Program sfnderiv | 
[SYNOPSIS]
sfnderiv < Fin.rsf > Fout.rsf order=1 length=5 scale=y axis=1
[COMMENTS]
This program implements Fornberg, 1988
paper for digital differentiators
of arbitrary order.

So, it computes first, second, n derivative along axis 1,2 or 3.

[PARAMETERS]
int     | axis | =1 |   | 	apply differentiator along axis, default is fast axis
int     | length | =5 |   | 	filter length, the lengthier the accurate, but also gets costlier
int     | order | =1 |   | 	order of the derivative, default first derivative
bool    | scale | =y |  [y/n] | 	scales by 1/d^order
[DIRECTORY]
user/ediazp
