Retrieving element index in spfun, cellfun, arrayfun, etc. in MATLAB

Question

Is there any way to retrieve the index of the element on which a function called by cellfun, arrayfun or spfun acts? (i.e

Answer 1

You can create a sparse matrix with linear_index filling instead of values.

Create A:

A(find(S))=find(S)

Then use A and S without spfun, e.g.: A.*S. This runs very fast.