#include <stdio.h>
#include <math.h>
#include <stdlib.h>

/* Simple Vegetation ratio */
double s_r(double redchan, double nirchan)
{
    double result;

    if ((redchan) == 0.0) {
        result = -1.0;
    }
    else {
        result = (nirchan / redchan);
    }
    return result;
}
