* Calling sequence: quadrature(npts, x, y)
 *
 *
 * Arguments:
 *    npts, double	number of points in tabulated function
 *    x[], double	array of independent variable values
 *    y[], double	array of dependent variable values
 *
 *--------------------------------------------------------------*/
 
double quadrature(npts, x, y)
double npts, x[], y[];
{
    int n, i;
    double integral = 0.0;

    n = (int) (npts - 0.9);
    for (i = 0; i < n; i++)
	integral += 0.5 * (x[i + 1] - x[i]) * (y[i] + y[i + 1]);
    return (integral);
}