Convert matrix back to array in EJML

Question

I have started using the EJML library for representing matrices. I will use the SimpleMatrix. I did not find two important things which I need. Perhaps somebody can help me identify if the following operations are possible and if yes, how this can be done:

1. Is it possible to convert a matrix back to a 1D double array (double[]) or 2D double array (double[][]) without just looping through all elements which would be very inefficient? I did not find a method for that. For example, Jeigen library provides a conversion to a 1D array (but I don't know how this is internally done).

2. Is it possible to delete a row or column?

By the way, does somebody know how EJML compares to Jeigen for large matrices in terms of runtime? EJML provides much more functionality and is much better documented but I'm a bit afraid in terms of runtime.

Answer 1

Manos' answer to the first question did not work for me. This is what I did instead:

public double[][] matrix2Array(SimpleMatrix matrix) {
    double[][] array = new double[matrix.numRows()][matrix.numCols()];
    for (int r = 0; r < matrix.numRows(); r++) {
        for (int c = 0; c < matrix.numCols(); c++) {
            array[r][c] = matrix.get(r, c);
        }
    }
    return array;
}

I don't know how it compares in performance to other methods, but it works fast enough for what I needed it for.