Question

I’ve been battling with this for some time and seem to be getting nowhere. The set up is so; I have a 2D array. For this array I need to iterate through each value and return the diagonal neighbours (5 values). These neighbours will be put into a new 1D [5] array and bubblesorted. The middle value (median) will then be returned and put into a new array of medians.

So far I have methods for extracting the diagonal neighbours:

    //get diagonals from original DEM

    double [] getDiagonals(int i, int j) {

        double [] tempArray = new double [5];

        tempArray[0] = data[i -1][j +1];
        tempArray[1] = data[i -1][j -1];
        tempArray[2] = data[i][j];
        tempArray[3] = data[i +1][j -1];
        tempArray[4] = data[i +1][j +1];


        return tempArray;
    }

I’ve then used this method in an iteration to get diagonals for each value in the original array:

        //get diagonals for each 

    double [] []   bubbles(){

        double [] [] datap = new double [298] [298];

        for (int i = 1; i < data.length; i++){
            for (int j = 1; j < data[i].length; j++) {
                if ((i > 0) && (j > 0)) {
                    if ((i < data.length-1) && (j  < data.length-1)){

                         double [] tempArray = getDiagonals(i, j);
//do something with the tempArray

I think this is where I’m coming unstuck. Through testing the getDiagonals method works fine. I’m struggling to get the tempArray out of the bubbles() method. If I set the output to be the tempArray it only returns the 5 values calculated for the bottom right corner of the original array.

I’ve tried calling other methods into the bubbles() method in order to do all the processing there and return a new array:

    //get diagonals for each 

    double [] []   bubbles(){

        double [] [] datap = new double [298] [298];

        for (int i = 1; i < data.length; i++){
            for (int j = 1; j < data[i].length; j++) {
                if ((i > 0) && (j > 0)) {
                    if ((i < data.length-1) && (j  < data.length-1)){

                         double [] tempArray = getDiagonals(i, j);
                         double sorted [] = sort(tempArray);
                         double median = sorted[2];


                            for (int z = 0; z < datap.length; z++){
                                for (int y = 0; y < datap[z].length; y++){
                                datap[z][y] = median;
                                }
                            }   



                    }
                }   
            }
        }
        return datap;
    }

Again this fails and the output datap is just zeros. The sort() method above passed out the diagonals to a bubble sort method (which I know works on its

I guess my question is how to process within a method that is iterating and populate a new array?

I hope this makes sense but if you need more details please let me know. And yes, the sort I’m using is a bubble sort. I know they are rubbish but this is for a course I’m doing so it has to be used. And yes, I’m pretty new to java.

Any help would be greatly appreciated (and I’ll even reference you if I need to use some code you provide 😉

Answer 1

Finally cracked it. To populate the whole array the following code works a peach.

//Diagonal to 1dArray and sorting

double [] [] bubbles()
{
    double [][] tempArray = new double [300][300];

    int y = 0;
    int z = 0;
    double median = 0;

    for (int i = 0; i < data.length; i++)
    {
        for (int j = 0; j < data[i].length; j++)
        {
            if ((i > 0) && (j > 0))
            {
                if ((i +1 < data[i].length) && (j +1 < data[j].length))
                {
                    double [] diagonals = getDiagonals(i, j);

                    //Need to sort here
                    median = diagonals[2];
                    tempArray[i][j] = median;
                }
            }
        }
    }
    return tempArray;
}

The sorting was taken out and I haven’t tested with it back in yet; but so far this is providing new values for all the cells in the temp array.