Question

我找到标准偏差的代码是错误的。我的代码应该找到用户输入的标准偏差。我输入了数字1 2 3，这组数字的标准偏差是1，但它打印10我哪里出错了。我也知道我有一堆未使用的变量，不介意它们。

import java.util.Scanner; 

public class readFromKeyboard { 

    public static void main(String[] args) { 


        Scanner input = new Scanner(System.in); 

        String inStr = input.next(); 
        int n;
        int i;
        int count=0; 
        int min = Integer.MAX_VALUE;
        int max = Integer.MIN_VALUE; 
        double average=0;
        int sum;
        double deviation = 0;
        int total;
        int temp = 0;



        while (!inStr.equals("EOL")) { 
          count++; 
          n = Integer.parseInt(inStr); 
          min = Math.min(min, n);
          max = Math.max(max, n);
          System.out.printf("%d ", n); 
          inStr = input.next(); 
          average += n;
          temp += Math.pow(n - average, 2);

        } 

        deviation = temp
        average = average/count;

        System.out.println("\n The average of these numbers is " + average);
        System.out.printf("The list has %d numbers\n", count); 
        System.out.printf("The minimum of the list is %d\n", min);
        System.out.printf("The maximum of the list is %d\n", max);
        System.out.printf("The standard deviation of the list is %d\n", temp);

        input.close(); 


    } 
}

Answer 1

import java.util.ArrayList;
import java.util.Scanner;

public class ReadFromKeyboard {

    public static void main(String[] args) {

        Scanner input = new Scanner(System.in);

        String inStr = input.next();
        int n = 0;
        int i;
        int count = 0;
        int min = Integer.MAX_VALUE;
        int max = Integer.MIN_VALUE;
        double average = 0;
        int sum;
        double deviation = 0;
        int total;
        double temp = 0;// correction here because it must store double or float value

        ArrayList<Integer> n1 = new ArrayList<Integer>();// i used this to store all entered values

        while (!inStr.equals("EOL")) {
            count++;
            n = Integer.parseInt(inStr);
            min = Math.min(min, n);
            max = Math.max(max, n);
            System.out.printf("%d ", n);
            n1.add(n);
            inStr = input.next();
            average += n;

        }

        average = average / count; // this will give you final average

        for (int j = 0; j < count; j++) {
            temp += Math.pow(n1.get(j) - average, 2);
        }
        //System.out.println("\n" + temp + " " + count);
        deviation = Math.sqrt(temp / count); // this is your standard deviation

        //System.out.println(deviation);

        System.out.println("\n The average of these numbers is " + average);
        System.out.printf("The list has %d numbers\n", count);
        System.out.printf("The minimum of the list is %d\n", min);
        System.out.printf("The maximum of the list is %d\n", max);
        System.out.println("The standard deviation of the list is " + deviation);

        input.close();

    }
}

Answer 2

定义一个变量的标准差here。你必须取观察值与集合平均值之差的平均值的平均值的平方根。

//in the loop
temp += Math.pow(n - average, 2)
//outside the loop
deviation = Math.pow(temp/count,0.5) //or alternatively Math.sqrt()

这应该可以满足您的需求。

我的标准偏差计算有什么问题？

2 个答案: