first_and_second_harmonic_function

photutils.isophote.first_and_second_harmonic_function(phi, c)[source]

Compute the harmonic function value used to calculate the corrections for ellipse fitting.

This function includes simultaneously both the first and second order harmonics:

\[f(phi) = c[0] + c[1]*\sin(phi) + c[2]*\cos(phi) + c[3]*\sin(2*phi) + c[4]*\cos(2*phi)\]
Parameters
phifloat or ndarray

The angle(s) along the elliptical path, going towards the positive y axis, starting coincident with the position angle. That is, the angles are defined from the semimajor axis that lies in the positive x quadrant.

cndarray of shape (5,)

Array containing the five harmonic coefficients.

Returns
resultfloat or ndarray

The function value(s) at the given input angle(s).