I want to solve the following task efficiently. I need to read data from S files (in my case S = 50000). Each file has T rows of 5 floats each. Here T=1000 is a time index and 5 is the dimension of a dynamical system. From each file I want to read the j coordinate and to assign its T values to a column in a matrix X. At the end of this process I'll have an X array or matrix of dimension T x S. How can I do this efficiently? When I use 'readdata' in order to read the Tx5 matrix from a single file into a list D, this is a fast process. But assigning, naively, the j column from this matrix to my matrix X, using a for loop,