Convert linear functions to matrix form

Obtaining the matrix representing a given linear function

As is well known, if f() is linear function then there exists a matrix A such that for any Y=f(X), where X and Y are array-valued input/output arguments, the operation can equivalently be expressed Y(:)=A*X(:). In MATLAB, we are often given linear operations f() in function form only, but need the matrix form to do linear algebraic manipulations: transpose, pseudo-inversion, etc...

The file FUNC2MAT in this submission computes the matrix A given a handle, fun, to any linear mapping from N-dimensional to M-dimensional space. An alternative and faster version LOCALFUNC2MAT is also available for certain types of linear transformations where impulse inputs have very localized responses in the output. Many image transformation functions like INTERPN, IMWARP, IMROTATE, etc... satisfy this property.

See the Examples tab for demonstrations of use.