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pythonc++sparse-matrixeigen

Sparse Random Matrix with Eigen

Is it possible to make a (sparse) matrix with the C++ Eigen library similar to this elegant python code I need to translate?

(np.random.rand(100,100)  < 0.1) * np.random.rand(100,100)

e.g. a matrix filled with a certain proportion of random values.

Solution

  • davidhigh's answer addresses the sparse requirement of your question. However, I don't think that your python code actually produces a sparse matrix, but rather a dense matrix with mostly zeros. A similarly elegant version for Eigen can be 

    MatrixXd mat;
mat2 = (MatrixXd::Random(5,5).array() > 0.3).cast<double>() * MatrixXd::Random(5,5).array();

    Note that this uses the standard C++ rand(), so may not be sufficiently "random", depending on your needs. You can also replace MatrixXd with MatrixXf if you prefer floats over doubles (change the cast<...>() as well).