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| spfun | Examples |
Apply function to nonzero sparse matrix elements
f = spfun('function',S)
The spfun function selectively applies a function to only the nonzero elements of a sparse matrix, preserving the sparsity pattern of the original matrix (except for underflow).
f = spfun('function',S)
evaluates function(S) on the nonzero elements of S. function must be the name of a function, usually defined in an M-file, which can accept a matrix argument, S, and evaluate the function at each element of S.
Functions that operate element-by-element, like those in the elfun directory, are the most appropriate functions to use with spfun.
Given the 4-by-4 sparse diagonal matrix
S = (1,1) 1 (2,2) 2 (3,3) 3 (4,4) 4
f = spfun('exp',S) has the same sparsity pattern as S:
f = (1,1) 2.7183 (2,2) 7.3891 (3,3) 20.0855 (4,4) 54.5982whereas
exp(S) has 1s where S has 0s.
full(exp(S))
ans =
2.7183 1.0000 1.0000 1.0000
1.0000 7.3891 1.0000 1.0000
1.0000 1.0000 20.0855 1.0000
1.0000 1.0000 1.0000 54.5982