Concatenate sparse matrices in Python using SciPy/Numpy

Question

What would be the most efficient way to concatenate sparse matrices in Python using SciPy/Numpy?

Here I used the following:

>>> np.hstack((X         


        

Answer 1

You can use the scipy.sparse.hstack to concatenate sparse matrices with the same number of rows (horizontal concatenation):

from scipy.sparse import hstack
hstack((X, X2))

Similarly, you can use scipy.sparse.vstack to concatenate sparse matrices with the same number of columns (vertical concatenation).

Using numpy.hstack or numpy.vstack will create an array with two sparse matrix objects.