Thread: Help with Multi-dimensional Arrays. Help needed urgently!

I am having trouble fixing and figuring out how to change my code. My out put is very off, and I was wondering if anyone could give me insight to why, maybe even pose a solution,

"Enter a 3-by-3 matrix row by row:
1 1 1
1 1 1
1 1 1
Sum of the major diagonal is 6.0
Sum of the values of the column are: 10.0
Sum of the values of the column are: 20.0
Sum of the values of the column are: 30.0 "

I have tried a lot of things, but not much has helped.
Thank you and any help is greatly appreciated.

Code is below:

 
    public static void main(String[] args) {
        double[][] m = new double[3][3];
        m = createArray();  
 
    }    
    private static double[][] createArray() { 
 
    Scanner input = new Scanner(System.in);
    double[][] matrix = new double[3][3];
    System.out.println("Enter a " + matrix.length + "-by-" + matrix[0].length +
                " matrix row by row: ");
    for (double[] m1 : matrix) {
        for (int j = 0; j < matrix[0].length; j++) {
 
            m1[j] = input.nextDouble();
 
        }
    } 
    System.out.println("Sum of the major diagonal is " + sumMajorDiagonal(matrix));
    sumColumn (matrix, 0); 
        return matrix;
    }  
 
 public static double sumColumn(double[][] matrix, int columnIndex){
 
   double total = 0;//problem lies here
   double sum = 0;
   int row = 0;
   int last = matrix[0].length;
   for(columnIndex = 0; columnIndex < matrix[row].length; columnIndex++) {
        //total += matrix[0][1] + [1][1];
        total += matrix[row][--last];
   System.out.println("Sum of the values of the column are: " + (columnIndex + 1)
        + sum);   
 }
 
      return sum;  
} 
 
public static double sumMajorDiagonal(double[][] m) {
 
    double total = 0.0;
    int last = m[0].length;
 
    for(int row = 0; row < m.length; row++) {
        total += m[row][row];
        total += m[row][--last];
}
  return total;    
 } 
}

You're not concerned about the sum of the major diagonal?

I don't understand the purpose for the variable 'last'. Can you describe what that does? Oh yeah, that reminds me: comments in your code would be nice, probably even helpful to you and certainly helpful to those reviewing your code.

You have too many things going on in some of your methods. Methods other than main() should do one thing. The one thing they do should be described by the name of the method, usually a verb or containing a verb. The one thing each method does should be done very well.

Thank you very much for the fast response.
my output needs to look some thing like this. like this:

"Enter a 3-by-3 matrix row by row:
Row 1: 1 2 3
Row 2: 5 6 7
Row 3: 9 1 3

The sum of the elements at Column 1 is 16
The sum of the elements at Column 2 is 9
The sum of the elements at Column 3 is 13

The sum of the elements along the major diagonal is 10"

My main plan of action is to first get the problem figured out with the sum of the columns and then later, tackle the major diagonal.
I am currently trying to figure out what is exactly wrong with my methods.....and what is causing this incorrect results to appear.

 
//Write a program that reads a 3 by 3 array of double values row by row, stores
//values into a two dimensional array of three rows by three columns
 
  public static void main(String[] args) {
        double[][] matrix = new double[3][3];// the 3 - 3 matrix
        matrix = createArray();  
 
    }    
    private static double[][] createArray() { 
 
    Scanner input = new Scanner(System.in);
    double[][] matrix = new double[3][3];
    System.out.println("Enter a 3-by-3 matrix row by row ");
    for (double[] m1 : matrix) {
    System.out.println("Row: ");
        for (int j = 0; j < matrix[0].length; j++) {
 
            m1[j] = input.nextDouble();
 
        }
    } 
    System.out.println("Sum of the major diagonal: " + sumMajorDiagonal(matrix));
    sumColumn (matrix, 0); 
        return matrix;
    }  
 
 public static double sumColumn(double[][] matrix, int columnIndex){
 
   double sum = 0;
   for (int column = 0; column < matrix.length; column++) {
      for (int row = 0; row < matrix[column].length; row++){
         sum += matrix[row][column];  
}
   System.out.println("Sum of 1st column is " + column + sum); 
} 
        return sum;
}
 
public static double sumMajorDiagonal(double[][] matrix) {
 
    double sum = 0.0;
    int last = matrix[0].length;
 
    for(int row = 0; row < matrix.length; row++) {
        sum += matrix[row][row];
        sum += matrix[row][--last];  //calculate the last value and ends 
}
return sum; 
}
}

this is the code where the summation is completed:
Thank you for your assistance

 public static double sumColumn(double[][] matrix, int columnIndex){
 
   double sum = 0;
   //below is the code to solve for the column sum/ summation
   for (int column = 0; column < matrix.length; column++)
   {
      for (int row = 0; row < matrix[column].length; row++)
      {
         sum += matrix[row][column];  
}
   System.out.println("Sum of 1st column is " + column + sum); 
} 
        return sum;
}

So, I solved it. Now I only need help with calculating the major diagonal

 public static double sumColumn(double[][] matrix, int column){
 
   int row;
   double sum = 0;
   //below is the code to solve for the column 
   for (column = 0; column < matrix[0].length; column++)
   {
    sum = 0;
   for (row = 0; row < matrix.length; row++)
    sum = sum + matrix[row][column];      
   System.out.println("Sum of column " + (column + 1) + " = " + sum);    
} 
        return sum;
}

This is the code that I am still working on. It calculated the diagonal twice instead of only once. Any insights.
Thank you very much for your patience and assistance, I am deeply appreciative.

the full code 
 
public static double sumMajorDiagonal(double[][] matrix) {
 
    double sum = 0.0;
    int last = matrix[0].length;
 
    for(int row = 0; row < matrix.length; row++) {
        sum += matrix[row][row];
        sum += matrix[row][--last];  //calculate the last value and ends 
}
return sum; 
}
}

Thanks, I finally solved my problem. I really appreciate all the help you have given me!
If it had not been for your insight it probably would have taken me much longer, thank you so much again.
-Vex