如何计算C ++或Java中的方差，中位数和标准差？

Question

我有一些双打（1.1,2,3,5）的向量。如何计算方差，中位数和标准偏差？

Java或C ++甚至伪代码都可以。

Answer 1

public class Statistics {
double[] data;
int size;

    public Statistics(double[] data) {
        this.data = data;
        size = data.length;
    }

    double getMean() {
        double sum = 0.0;
        for(double a : data)
            sum += a;
        return sum/size;
    }

    double getVariance() {
        double mean = getMean();
        double temp = 0;
        for(double a :data)
            temp += (a-mean)*(a-mean);
        return temp/(size-1);
    }

    double getStdDev() {
        return Math.sqrt(getVariance());
    }

    public double median() {
       Arrays.sort(data);
       if (data.length % 2 == 0)
          return (data[(data.length / 2) - 1] + data[data.length / 2]) / 2.0;
       return data[data.length / 2];
    }
}