CODEWITHSUNDEEP
javaarrays
user7461114
user7461114

Reputation:

Finding First Quartile and Third Quartile in integer array using java

public class tryA {

  public static void main(String[] args) {
  int[] intArray= new int[41];
  System.out.println(intArray[intArray.length/2]);

}

How to find the Lower Quartile (Q1) and Third Quartile (Q3) for my integer Array intArray? Providing that the size of array might be a variables.

P.S: It is used to find the outlier of the array.

Upvotes: 3

Views: 8696

Answers (3)

vasilis vittis
vasilis vittis

Reputation: 31

My solution is plug and play! You just give an array (val) of double numbers and it gives you back an array with 3 doubles Q1 in position 0, Q2 in position 1 and Q3 in position 2.

public double[] Quartiles(double[] val) {
    double ans[] = new double[3];

    for (int quartileType = 1; quartileType < 4; quartileType++) {
        float length = val.length + 1;
        double quartile;
        float newArraySize = (length * ((float) (quartileType) * 25 / 100)) - 1;
        Arrays.sort(val);
        if (newArraySize % 1 == 0) {
            quartile = val[(int) (newArraySize)];
            } else {
            int newArraySize1 = (int) (newArraySize);
            quartile = (val[newArraySize1] + val[newArraySize1 + 1]) / 2;
             }
        ans[quartileType - 1] =  quartile;
    }
    return ans;
}

Upvotes: 1

Timo Richter
Timo Richter

Reputation: 174

You can derive this from the percentiles. For calculating percentiles in Java, there is a nice solution: Calculate percentile from a long array?

Upvotes: 0

dat3450
dat3450

Reputation: 954

I believe this is what you are looking for, change the quartile variable at the top of the code to change between Q1, Q2, Q3 and Q4.

import java.util.Arrays;

public class ArrayTest
{
    public static void main(String[] args)
    {
        //Specify quartile here (1, 2, 3 or 4 for 25%, 50%, 75% or 100% respectively).
        int quartile = 1;

        //Specify initial array size.
        int initArraySize = 41;

        //Create the initial array, populate it and print its contents.
        int[] initArray = new int[initArraySize];
        System.out.println("initArray.length: " + initArray.length);
        for (int i=0; i<initArray.length; i++)
        {
            initArray[i] = i;
            System.out.println("initArray[" + i + "]: " + initArray[i]);
        }

        System.out.println("----------");

        //Check if the quartile specified is valid (1, 2, 3 or 4).
        if (quartile >= 1 && quartile <= 4)
        {
            //Call the method to get the new array based on the quartile specified.
            int[] newArray = getNewArray(initArray, quartile);
            //Print the contents of the new array.
            System.out.println("newArray.length: " + newArray.length);
            for (int i=0; i<newArray.length; i++)
            {
                System.out.println("newArray[" + i + "]: " + newArray[i]);
            }
        }
        else
        {
            System.out.println("Quartile specified not valid.");
        }
    }

    public static int[] getNewArray(int[] array, float quartileType)
    {
        //Calculate the size of the new array based on the quartile specified.
        int newArraySize = (int)((array.length)*(quartileType*25/100));
        //Copy only the number of rows that will fit the new array.
        int[] newArray = Arrays.copyOf(array, newArraySize);
        return newArray;
    }
}

Upvotes: 0

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