Approximation

The Approximation error (benaderingsfout) is the difference between a calculated value and the real value. By dividing it by the real value you get the relative error. A bit relative error indicates bad calculation. The largest relative error between two arrays as percentage:

np.mean(abs(calculated - real))                  # Average of the absolute errors 
np.mean(abs(calculated - real) / real )          # Average of the differences relative to the real values
np.mean(abs(calculated - real) / real ) * 100    # The relative error as percentage.