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pythonscipysparse-matrix

How to merge two csr_matrix into one?

I have problems using scipy.sparse.csr_matrix:

for instance: 

a = csr_matrix([[1,2,3],[4,5,6]])
b = csr_matrix([[7,8,9],[10,11,12]])

how to merge them into

[[1,2,3],[4,5,6],[7,8,9],[10,11,12]]

I know a way is to transfer them into numpy array first:

csr_matrix(numpy.vstack((a.toarray(),b.toarray())))

but it won't work when the matrix is huge and sparse, because the memory would run out.

so are there any way to merge them together in csr_matrix?

any answers are appreciated!

Solution

  • scipy.sparse has it's own stack-methods. You can use them directly on your sparse matrices.

    import scipy.sparse as sp

a = sp.csr_matrix([[1,2,3],[4,5,6]])
b = sp.csr_matrix([[7,8,9],[10,11,12]])
c = sp.vstack((a,b))  # NOT np.vstack