ross.c - 1 year ago 93

Java Question

creating a program that enables the user to enter an integer N, then reads N double values, and prints their mean (average value) and sample standard deviation (square root of the sum of the squares of their differences from the average, divided by N - 1).

So far I have this code

`import java.util.Scanner;`

public class AVGDevi

{

public static void main(String[] args)

{

Scanner input = new Scanner(System.in);

double x;

double sum = 0;

double average = 0;

double dev = 0;

double var = 0;

double sqrx = 0;

int n = 0;

do

{

System.out.println("Enter an integer:");

x = input.nextInt();

if (x == -1)

{

break;

}

sum += x;

n++;

average = sum / n;

sqrx += Math.pow(x-average,2);

var = sqrx / (n-1);

dev = Math.sqrt(var);

} while (x<= 0);

System.out.println("Average: " + average);

System.out.println("Deviation: " + dev);

}

}

test case:

`5`

1

2

3

4

5

Currently getting this output

`Enter an integer:`

Average: 5.0

Deviation: NaN

Output should be

`Enter an integer: Enter a number: Enter a number: Enter a number: Enter a number: Enter a number: Average value is: 3.0`

The standard deviation is: 1.58

I'm not 100% sure what I'm doing wrong any help would be great :D !

Answer Source

You can use only while loop instead of do-while loop, as following:

```
public static void main(String[] args)
{
Scanner input = new Scanner(System.in);
double y=-1;
double sum = 0;
double average = 0;
double dev = 0;
double var = 0;
double sqrx = 0;
int n = 0;
System.out.println("Enter an integer:");
y = input.nextInt();
double z=y;
int i=0;
double x[] = new double[(int)z];
while(y-->0){
x[i] = input.nextDouble();
sum += x[i];
i++;
n++;
average = sum / n;
}
i=0;
while(z-->0){
sqrx += Math.pow(x[i]-average,2);
i++;
}
var = sqrx / (n-1);
dev = Math.sqrt(var);
System.out.println("Average: " + average);
System.out.println("Deviation: " + dev);
}
```