Guide to Madagascar programs

sfstack: Stack a dataset over one of the dimensions.

sfstack < in.rsf > out.rsf scale= axis=2 rms=n norm=y min=n max=n prod=n

This operation is adjoint to sfspray.

int	axis=2		which axis to stack
bool	max=n	[y/n]	If y, find maximum instead of stack. Ignores rms and norm.
bool	min=n	[y/n]	If y, find minimum instead of stack. Ignores rms and norm.
bool	norm=y	[y/n]	If y, normalize by fold.
bool	prod=n	[y/n]	If y, find product instead of stack. Ignores rms and norm.
bool	rms=n	[y/n]	If y, compute the root-mean-square instead of stack.
floats	scale=		optionally scale before stacking [n2]

While sfspray adds a dimension to a hypercube, sfstack effectively removes one of the dimensions by stacking over it. Here are some examples:

bash$ sfmath n1=5 n2=3 output=x1+x2 > test.rsf
bash$ < test.rsf sfdisfil
   0:             0            1            2            3            4
   5:             1            2            3            4            5
  10:             2            3            4            5            6
bash$ < test.rsf sfstack axis=2 | sfdisfil
   0:           1.5            2            3            4            5
bash$ < test.rsf sfstack axis=1 | sfdisfil
   0:           2.5            3            4

Why is the first value not 1 (in the first case) or 2 (in the second case)? By default, sfstack normalizes the stack by the fold (the number of non-zero entries). To avoid normalization, use norm=n, as follows:

bash$ < test.rsf sfstack norm=n | sfdisfil 
   0:             3            6            9           12           15

sfstack can also compute root-mean-square values as well as minimum and maximum values.

bash$ < test.rsf sfstack rms=y | sfdisfil
   0:         1.581         2.16        3.109        4.082        5.066
bash$ < test.rsf sfstack min=y | sfdisfil
   0:             0            1            2            3            4
bash$ < test.rsf sfstack axis=1 max=y | sfdisfil 
   0:             4            5            6

Guide to Madagascar programs