Program sfderiv3 | Second order derivative along axis
[SYNOPSIS]
sfderiv3 < in.rsf > out.rsf axis=1 operator=2
[COMMENTS]

int axis=[1] axis to differentiate

int operator=[2] 1 backward, 2 centered, 3 forward



[PARAMETERS]
int     | axis | =1 |   | 	
int     | operator | =2 |   | 	
[DIRECTORY]
user/ediazp
