Compute the index of an 1D array of spherical harmonic coefficients corresponding to i, l, and m.
index = YilmIndex (i, l, m)
index : output, integer
: Index of an 1D array of spherical harmonic coefficients corresponding to i, l, and m.
i : input, integer
: 1 corresponds to the cosine coefficient cilm(1,:,:), and 2 corresponds to the sine coefficient cilm(2,:,:).
l : input, integer
: The spherical harmonic degree.
m : input, integer
: The angular order.
YilmIndexVector will calculate the index of a 1D vector of spherical harmonic coefficients corresponding to degree l, angular order m and i (1 = cosine, 2 = sine). The index is given by l**2+(i-1)*l+m+1.