﻿ Java exercises and solutions: Array in statistics information

# Java exercises and solutions: Array in statistics information

## Java arrays: statistics information

Exercise: Write a Java program to answer about the statistical information such as arithmetic mean, median, mode, and standard deviation of an integer data set. The data points are input by the user from keyboard. This program will display the output similar to the one shown below: If you are not sure about statistical information such as arithmetic mean, median, mode, and standard deviation, you will need to read this page:

Solution:

import java.util.Scanner;

public class StatisticsInfo
{
public static void main(String[] args)
{
showStatistics();
}

static void showStatistics(){
//

int n;
float mean,median,std;
Scanner sc=new Scanner(System.in);
System.out.print("Enter number of data points:");
n=sc.nextInt();
if (n < 3)
{
System.out.println("The number of data points should be greater than 2.");

}
else
{

//declare an array of n size to store integral data points
int[] dataset = new int[n];
//allow user inputs
int i = 0;
for (i = 0; i < n; i++)
{
System.out.print("["+i+"]:");
dataset[i] = sc.nextInt();
}

//sort the data set
bubblesort(dataset, n);

//calculate the mean
int sum = 0;
int j = 0;
while (j < n)
{
sum = sum + dataset[j];
j++;
}

mean = (float)sum / n;

//calculate median
//If n is odd, median=dataset[n/2]
//If n is even, median=(dataset[n/2]+dataset[1+n/2])/2
//The index of array starts from 0, so you need to subtract 1 from the indices used in calculating the median
if (n % 2 != 0) median = dataset[n / 2];
else median = (dataset[(n / 2) - 1] + dataset[n / 2]) / (float)2;

//calculate the mode
int[][] mode = new int[n];
//initialize 2D array storing numbers of occurences, and values
for (i = 0; i < 2; i++)
for (j = 0; j < n; j++) mode[j][i] = 0;
mode = 1;

for (i = 0; i < n; i++)
for (j = 0; j < n - 1; j++)
if (dataset[i] == dataset[j + 1]) { ++mode[i]; mode[i] = dataset[i]; }

int max;
int k = 0;
max = mode;
for (j = 0; j < n; j++)
if (max < mode[j]) { max = mode[j]; k = j; }

//calculate standard deviation,std
float temp = 0.0f;

for (j = 0; j < n; j++)
{
temp = temp + (float)Math.pow(dataset[j] - mean, 2);
}

std = (float)Math.sqrt(temp / (n - 1));

//Show results

System.out.println("Statistical Information:");
System.out.println("===============================");
System.out.println("Arithmetic mean:"+mean);
System.out.println("Median:"+median);
if (mode[k] != 0)
System.out.println("Mode:"+ mode[k]);
else System.out.println("Mode: no mode");
System.out.println("Standard deviation:"+std);

}

//

}

}

### Comments TomaszThis Solution is not working2016-12-22

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