title: Element wise exp() of scipy sparse matrix
body: <p>I have a very big <strong>sparse csc_matrix</strong> <code>x</code>. I want to do elementwise exp() on it. Basically what I want is to get the same result as I would have got with <code>numpy.exp(x.toarray())</code>. But I can't do that(my memory won't allow me to convert the sparse matrix into an array). Is there any way out? Thanks in advance!</p>