fit_upper_harmonic¶
- photutils.isophote.fit_upper_harmonic(phi, intensities, order)[source]¶
Fit upper harmonic function to a set of (angle, intensity) pairs.
With
order
set to 3 or 4, the resulting amplitudes, divided by the semimajor axis length and local gradient, measure the deviations from perfect ellipticity.The harmonic function that is fit is:
\[y(phi, order) = y0 + An*\sin(order*phi) + Bn*\cos(order*phi)\]- 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.
- intensities
ndarray
The intensities measured along the elliptical path, at the angles defined by the
phi
parameter.- orderint
The order of the harmonic to be fitted.
- phifloat or
- Returns:
- y0, An, Bnfloat
The fitted harmonic values.