morphology.py 文件源码

def eta(radii, phot):
    """
    eta = I(r) / \bar{I}(<r)

    radii -- 1d array of aperture photometry radii
    phot -- 1d array of aperture photometry fluxes

    this is currently calculated quite naively, and probably could be done better
    """
    phot_area = np.pi * radii**2
    phot_area_diff = np.ediff1d(phot_area, to_begin=phot_area[0])
    I_bar = phot / (phot_area)
    I_delta_r = np.ediff1d(phot, to_begin=phot[0]) / phot_area_diff
    I_r = (I_delta_r[:-1] + I_delta_r[1:]) / 2 #lost last array element here
    I_r = np.append(I_r, I_delta_r[-1]) #added it back in here
    eta = I_r / I_bar
    return eta