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I am currently trying to count the number of times that a value occurs in each column of a 10 x 10 matrix with Java.

I can make it count the times in each row, but I am having a rough time with the column counts.

Thanks for your help, I am new to this site and to Java.

import java.util.Random;
import static java.lang.System.*;

public class Problem710 {

    public static void main(String[] args) {
        int[][] randArr = new int[10][10];
        double count = 0;
        for (int i = 0; i < randArr.length; ++i) {
            for (int j = 0; j < randArr[0].length; ++j) {
                randArr[i][j] = getRandInt(0, 1);
                count += randArr[i][j];

                out.print(randArr[i][j]);

            }
            out.println();
        }


        double averagePerRow = count / 10;
        out.println(averagePerRow);

    }

    public static int getRandInt(int min, int max) {
        Random rand = new Random();
        return rand.nextInt(max - min + 1);
    }
}
Andrew Thompson
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user3052720
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  • Welcome to stackoverflow, but please **post** some of your **code**.. – Kuba Spatny Nov 30 '13 at 18:04
  • What have you tried? By the way, because you are new, here a good start point to formulate a better question http://stackoverflow.com/questions/how-to-ask – emecas Nov 30 '13 at 18:08
  • I just added what code I have that will get the average number of 1's in a row, now I need to make it do the same thing with the columns. – user3052720 Nov 30 '13 at 18:11
  • Isn't the average the same for rows and columns?? – Kuba Spatny Nov 30 '13 at 18:18
  • not the average number of times that the value 1 occurs.... that is what is getting me stuck – user3052720 Nov 30 '13 at 18:20
  • @user3052720 the average will always be the same for rows and columns in your case. But you can just switch the counting variables in the nested for loops and then change the order in the array position to get columns instead of rows. – Michael Yaworski Nov 30 '13 at 18:26

2 Answers2

0

an approach would be to convert the columns to rows and count it as usual ! That should do it ! This is how you exchange row and cols ... 

    int [] [] lol =


        {
            {1,1,1,1,1},
            {2,2,2,2,2},
            {3,3,3,3,3},
            {4,4,4,4,4},
            {5,5,5,5,5}



        };
    int [][]  dup = new int [lol.length][lol[0].length];
    for (int i = 0; i < lol.length; i++) {
        for (int j = 0; j < lol[0].length; j++) {
            dup[j][i] = lol[i][j];
        }
    }
}

}

Prashant Ghimire
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0

The wording is not clear to me, but if you don't want to know occurrences for the whole matrix, but each individual column, then use this: 

int[][] matrix = new int[10][10];
int counter = 0;
int column = 0; // which column
int what = 10;
for(int i = 0; i < matrix.lenght; i++){
   if(matrix[i][column] == what) counter++
}

EDIT:

let's rewrite the matrix, so that 1 means true (there's the number you're looking for) and 0 means false. So for instance which has 1s only in the last row

|0 0 0 0|
|0 0 0 0|
|0 0 0 0|
|1 1 1 1|

  • the average for rows is (0+0+0+4)/4 = 1

  • the average for columns is (1+1+1+1)/4 = 1

I really can't see how the average could be different.

Kuba Spatny
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