Method std

src/accelerometer/java/AccStats.java:295–307

(double[] vals, double mean)

    // standard deviation
    public static double std(double[] vals, double mean) {
        if (vals.length == 0) {
            return Double.NaN;
        }
        double var = 0; // variance
        double len = vals.length; // length
        for (int i = 0; i < len; i++) {
            if (!Double.isNaN(vals[i])) {
                var += Math.pow((vals[i] - mean), 2);
            }
        }
        return Math.sqrt(var / len);
    }


    // same as above but matches R's (n-1) denominator (Bessel's correction)