Hi Eigen Community,

After I've diagonalized a matrix using:

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Eigen::SelfAdjointEigenSolver<Eigen::MatrixXd> eigOut(A);

I want to multiply each eigenvalue by some value and overwrite the original value.

I tried looping through each eigenvalue and then assigning the value. For example:

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for (int i=0; i< eigOut.eigenvalues().rows(); i++){
     eigOut.eigenvalues().row(i)*=i;
}


However, that refused to compile. Can anybody tell me how I should be accessing the eigenvalue itself and then be able to overwrite the pre-existing value?

Thanks!

.eigenvalues() returns a const reference, you need to copy them to your own vector before modifying them:

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VectorXd eigvals = eigOut.eigenvalues();
...
eigvals(i) *= i