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# Construct Sparse Matrix in Matlab from Compressed Sparse Column (CSC) format

user43833
1#
user43833 Published in September 20, 2018, 10:22 pm

I have a large sparse matrix (~5 billion non-zero values) in Python, stored in the csc_matrix format. I need to open it as a sparse matrix in Matlab. savemat apparently cannot save data of this size (seems to be capped at ~5GB), so I am resorting to saving it as an hdf5 file, as detailed here. However, I am having trouble opening it in matlab.

Given these three vectors: data, indices, indptr, whose meaning is explained:

standard CSC representation where the row indices for column i are stored in indices[indptr[i]:indptr[i+1]] and their corresponding values are stored in data[indptr[i]:indptr[i+1]].

How can I construct this matrix in Matlab? I can open these three vectors in Matlab using h5read no problem, but I don't know how to use them to construct the sparse matrix. This is not the format of the sparse command I usually use to construct a sparse matrix.

• As a stop gap step I'd try the transfer using the coo format, data, rows, cols (adjusted for the 0/1 index start). It won't be as compact, but it is probably more compatible. Compared to scipy, MATLAB seems to hide a lot of the sparse format details. – hpaulj Mar 25 '17 at 21:27
• @hpaulj that is a huge help, thank you. – The_Anomaly Mar 25 '17 at 21:47
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