Sparse Matrix Assignment becomes very slow in Matlab

Question

I am filling a sparse matrix P (230k,290k) with values coming from a text file which I read line by line, here is the (simplified) code

while ...
                    


        

Answer 1

By far the fastest way to generate a sparse matrix wihtin matlab is to load all the values in at once, then generate the sparse matrix in one call to sparse. You have to load the data and arrange it into vectors defining the row and column indices and values for each filled cell. You can then call sparse using the S = sparse(i,j,s,m,n) syntax.