Compute the index of an array corresponding to degree l and angular order m.

## Usage

index = PlmIndex (l, m)

## Parameters

index : function output, integer
Index of an array of associated Legendre functions corresponding to degree l and angular order m.
l : input, integer
The spherical harmonic degree.
m : input, 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 is equal to l*(l+1)/2+m+1.