给定类型为scipy.sparse.coo_matrix的矩阵，如何确定每行最大值的索引和值? [英] Given a matrix of type `scipy.sparse.coo_matrix` how to determine index and value of maximum of each row?

问题描述

给出形状为1.000.000 x 70.000的类型为scipy.sparse.coo_matrix的稀疏矩阵R，我发现了

Given a sparse matrixR of type scipy.sparse.coo_matrix of shape 1.000.000 x 70.000 I figured out that

row_maximum = max(R.getrow(i).data)

将给我第i行的最大值.

will give me the maximum value of the i-th row.

我现在需要的是与值row_maximum对应的索引.

What I need now is the index corresponding to the value row_maximum.

有什么想法可以实现这一目标吗?

Any ideas how to achieve that?

谢谢您的任何建议！

推荐答案

getrow(i)返回1 x n CSR矩阵，该矩阵具有indices属性，该属性给出data属性中相应值的行索引. (我们知道形状是1 x n，因此我们不必处理indptr属性.)因此这将起作用:

getrow(i) returns a 1 x n CSR matrix, which has an indices attribute that gives the row indices of the corresponding values in the data attribute. (We know the shape is 1 x n, so we don't have to deal with the indptr attribute.) So this will work:

row = R.getrow(i)
max_index = row.indices[row.data.argmax()] if row.nnz else 0

我们必须分别处理row.nnz为0的情况，因为如果row.data为空数组，则row.data.argmax()将引发异常.

We have to deal with the case where row.nnz is 0 separately, because row.data.argmax() will raise an exception if row.data is an empty array.

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