java计算方差、标准差(均方差)实例代码

 //方差s^2=[(x1-x)^2 +...(xn-x)^2]/n 或者s^2=[(x1-x)^2 +...(xn-x)^2]/(n-1) public static double Variance(double[] x) { int m=x.length; double sum=0; for(int i=0;i

 //BigDecimal 的sqrt方法 private static BigDecimal sqrt(BigDecimal num) { if (num.compareTo(BigDecimal.ZERO) <0) { return BigDecimal.ZERO; } BigDecimal x = num.divide(new BigDecimal("2"), MathContext.DECIMAL128); while (x.subtract(x = sqrtIteration(x, num)).abs().compareTo(new BigDecimal("0.0000000000000000000001")) > 0) ; return x; } private static BigDecimal sqrtIteration(BigDecimal x, BigDecimal n) { return x.add(n.divide(x, MathContext.DECIMAL128)).divide(new BigDecimal("2"), MathContext.DECIMAL128); }