使用java计算数组方差和标准差 觉得有用的话,欢迎一起讨论相互学习~
首先给出方差和标准差的计算公式
代码 public class Cal_sta { double Sum(double[] data) { double sum = 0; for (int i = 0; i < data.length; i++) sum = sum + data[i]; return sum; } double Mean(double[] data) { double mean = 0; mean = Sum(data) / data.length; return mean; } // population variance 总体方差 double POP_Variance(double[] data) { double variance = 0; for (int i = 0; i < data.length; i++) { variance = variance + (Math.pow((data[i] - Mean(data)), 2)); } variance = variance / data.length; return variance; } // population standard deviation 总体标准差 double POP_STD_dev(double[] data) { double std_dev; std_dev = Math.sqrt(POP_Variance(data)); return std_dev; } //sample variance 样本方差 double Sample_Variance(double[] data) { double variance = 0; for (int i = 0; i < data.length; i++) { variance = variance + (Math.pow((data[i] - Mean(data)), 2)); } variance = variance / (data.length-1); return variance; } // sample standard deviation 样本标准差 double Sample_STD_dev(double[] data) { double std_dev; std_dev = Math.sqrt(Sample_Variance(data)); return std_dev; }} 测试代码 public class testcal_sta { public static void main(String arg[]) { Cal_sta cal = new Cal_sta(); double[] testdata = {2, 4, 6, 7, 8, 9, 12, 36}; System.out.println("总和Sum " + cal.Sum(testdata)); System.out.println("平均值Mean " + cal.Mean(testdata)); System.out.println("总体方差Population Variance " + cal.POP_Variance(testdata)); System.out.println("总体标准差Population STD_dev " + cal.POP_STD_dev(testdata)); System.out.println("样本方差Sample Variance " + cal.Sample_Variance(testdata)); System.out.println("样本标准差Sample STD_dev " + cal.Sample_STD_dev(testdata)); }} 结果
对比