Numpy error: Singular matrix

Question

What does the error Numpy error: Matrix is singular mean specifically (when using the linalg.solve function)? I have looked on Google but couldn't find anything that made it clear when this error occurs.

Answer 1

A singular matrix is one that is not invertible. This means that the system of equations you are trying to solve does not have a unique solution; linalg.solve can't handle this.

You may find that linalg.lstsq provides a usable solution.

Answer 2

This function inverts singular matrices as well using numpy.linalg.lstsq:

def inv(m):
    a, b = m.shape
    if a != b:
        raise ValueError("Only square matrices are invertible.")

    i = np.eye(a, a)
    return np.linalg.lstsq(m, i)[0]