public static double devsq(double[] v) {double r = Double.NaN;if (v!=null && v.length >= 1) {double m = 0;double s = 0;int n = v.length;for (int i=0; i<n; i++) {s += v[i];}m = s / n;s = 0;for (int i=0; i<n; i++) {s += (v[i]- m) * (v[i] - m);}r = (n == 1)? 0: s;}return r;}