Compute the index of a array of Legendre functions corresponding to degree l and angular order m.

## Usage

index = PlmIndex (l, m)

## Returns

index : integer
Index of an array of associated Legendre functions corresponding to degree l and angular order m.

## Parameters

l : integer
The spherical harmonic degree.
m : integer
The angular order.

## Description

PlmIndex will calculate the index of an array of associated Legendre functions corresponding to degree l and angular order m. The input arrays are generated by routines such as PlmBar, PlmBar_d1, PlmSchmidt, PlmSchmidt_d1, PlmON, PlmON_d1, PLegendreA, and PLegendreA_d1. The array index in Python is equal to l*(l+1)/2+m.