I have a matrix mat of type Matrix<double, Dynamic, Dynamic>. Is there a way to return the same size matrix whose elements are the result of element wise exponent of the mat matrix? I need like this: resultMatrix = exp(mat).

Yes, you have to move the "array" world, e.g.:

res = mat.array().exp();

or

res = exp(mat.array());


See: http://eigen.tuxfamily.org/dox-devel/gr ... Class.html