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POScipy Sparse Matrices - Inconsistent Sums
 

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  1. POScipy Sparse Matrices - Inconsistent Sums
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    <p>I have a sparse matrix that I arrived at through a complicated bunch of calculations which I cannot reproduce here. I will try to find a simpler example of this.</p> <p>For now, does anyone know how it might be (even remotely) possible that I could have a sparse matrix <code>X</code> with the property that:</p> <pre><code>In [143]: X.sum(0).sum() Out[143]: 131138 In [144]: X.sum() Out[144]: 327746 In [145]: X.sum(1).sum() Out[145]: 327746 In [146]: type(X) Out[146]: scipy.sparse.csr.csr_matrix </code></pre> <p>My only guess is that if I want to sum columns correctly, I need to first cast the matrix as csc -- which makes sense. Although one would think that the sparse package would handle column sums gracefully (or throw an error) instead of just giving a WRONG answer.</p> <p>After more thought, I tried the following:</p> <pre><code>In [164]: X.tocsr().sum(0).sum() Out[164]: 131138 In [165]: X.tocsc().sum(0).sum() Out[165]: 131138 In [166]: X.tocoo().sum(0).sum() Out[166]: 131138 In [167]: X.tolil().sum(0).sum() Out[167]: 131138 In [168]: X.todok().sum(0).sum() Out[168]: 131138 In [169]: X.shape Out[169]: (196980, 43) In [170]: X Out[170]: &lt;196980x43 sparse matrix of type '&lt;type 'numpy.uint16'&gt;' with 70875 stored elements in Compressed Sparse Row format&gt; In [172]: X.todense().sum(0) Out[172]: matrix([[170726, 1041, 117398, 3526, 13202, 3585, 2355, 1895, 1392, 2189, 2070, 2603, 1676, 496, 1194, 933, 129, 529, 544, 256, 7, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0]], dtype=uint64) In [173]: X.sum(0) Out[173]: matrix([[39654, 1041, 51862, 3526, 13202, 3585, 2355, 1895, 1392, 2189, 2070, 2603, 1676, 496, 1194, 933, 129, 529, 544, 256, 7, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0]], dtype=uint16) </code></pre> <p>I should add some more context: the matrix has only non-negative entries (they are counts). In particular there were two sparse count matrices <code>A</code> and <code>B</code> which I multiplied together to get <code>X</code>.</p>
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      1. POScipy Sparse Matrices - Inconsistent Sums
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    1. COSomething seems very wrong here...
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      1. POScipy Sparse Matrices - Inconsistent Sums
      1. USAndy Hayden
    2. COMaybe the **scipy mailing list** is more appropriate for such a question? Sounds like a bug to me. **What answer do you expect to get here**?
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      1. POScipy Sparse Matrices - Inconsistent Sums
      1. USAnony-Mousse
    3. COOk-- will try the mailing list. Wasn't sure if perhaps there was something else I was missing. But also -- if anyone has any insight into how this might be possible (and what I mistaken assumptions I might be making) -- that would be awesome.
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      1. POScipy Sparse Matrices - Inconsistent Sums
      1. USgabe
 

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