Question

JAVA

Write a method that returns the sum of all the elements in a specified column in a matrix using

the following header:

public static double sumColumn(double [][] m, int columnIndex)

Write another method that returns the sum of all the elements in a specified row in a matrix using

the following header:

public static double sumRow( double [][] m, int rowIndex)

Write a test program that reads a 3-by-4 matrix and displays the sum of each column and sum of each row.

the result should print the sum of both the row and column respectively

this is what the result should look like

Enter a 3 by 4 matrix row by row:

1.5 2 3 4

5.5 6 7 8

9.5 1 3 1

Sum of the elements at column 0 is 16.5

Sum of the elements at column 1 is 9.0

Sum of the elements at column 2 is 13.0

Sum of the elements at column 3 is 13.0

Sum of the elements at row 0 is 10.5

Sum of the elements at row 1 is 26.5

Sum of the elements at row 2 is 14.5

Answer 1

import java.util.Scanner;

public class SumRowsColumns {

    public static double sumColumn(double[][] m, int columnIndex) {
        double sum = 0;
        for (int i = 0; i < m.length; i++) {
            sum += m[i][columnIndex];
        }
        return sum;
    }

    public static double sumRow(double[][] m, int rowIndex) {
        double sum = 0;
        for (int i = 0; i < m[0].length; i++) {
            sum += m[rowIndex][i];
        }
        return sum;
    }

    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        System.out.println("Enter a 3 by 4 matrix row by row:");
        double[][] m = new double[3][4];
        for (int i = 0; i < m.length; i++) {
            for (int j = 0; j < m[i].length; j++) {
                m[i][j] = in.nextDouble();
            }
        }
        for (int i = 0; i < m[0].length; i++) {
            System.out.println("Sum of the elements at column " + i + " is " + sumColumn(m, i));
        }
        for (int i = 0; i < m.length; i++) {
            System.out.println("Sum of the elements at row " + i + " is " + sumRow(m, i));
        }
        in.close();
    }
}