Deleting columns from multidimensional array

Question

_{Thursday, May 28, 2015 10:05 AM}

Hello,

I wish to delete several columns from a large multidimensional (2) array into a smaller array (I realize that I cannot simply delete columns in a MD Array and must copy it into a new one). Now I have searched all over the net for example code to do this but several I have tried have all had bugs in them. Has anyone got a working example of how I can reduce (delete) 1 or more columns from a multidimensional Array? I have tried I think nearly all examples currently available on the Net for this and None of them work properly.

All replies (5)

_{Thursday, May 28, 2015 11:01 AM ✅Answered | 1 vote}

Hi,

You can use this method to select columns from two dimensional array

private T[,] ResizeArray<T>(T[,] original, int[] indices)
        {
            var newArray = new T[original.GetLength(0), indices.Length];
            int minRows = original.GetLength(0);
            int minCols = Math.Min(indices.Length, original.GetLength(1));
            for (int i = 0; i < minRows; i++)
            {
                for (int j = 0; j < minCols; j++)
                    newArray[i, j] = original[i, indices[j]];
            }
            return newArray;
        }

lets say you have this array

string[,] values = new string[,] { { "item11", "item12", "item13" }, { "item21", "item22", "item23" } };

and you need to remove the middle column

int[] indices = new int[] { 0, 2 };
string[,] newArray = ResizeArray<string>(values, indices);

If this answer was helpful please remember to close your threads by marking helpful posts as answer

Fares

_{Thursday, May 28, 2015 12:18 PM ✅Answered | 1 vote}

If I understand your problem, I have modified the method to get the indices of the columns those you need to remove

private T[,] ResizeArray<T>(T[,] original, int[] columnsToRemove)
        {
            var newArray = new T[original.GetLength(0), original.GetLength(1)-columnsToRemove.Length];
            int minRows = original.GetLength(0);
            int minCols = Math.Min(columnsToRemove.Length, original.GetLength(1));
            for (int i = 0; i < minRows; i++)
            {
                int currentColumn = 0;
                for (int j = 0; j < original.GetLength(1); j++)
                {
                    if (columnsToRemove.Contains(j) == false)
                    {
                        newArray[i, currentColumn] = original[i, j];
                        currentColumn++;
                    }
                }
            }
            return newArray;
        }

string[,] values = new string[,] { { "item11", "item12", "item13" }, { "item21", "item22", "item23" } };
            int[] indices = new int[] { 1 };
            string[,] newArray = ResizeArray<string>(values, indices);

this will remove the column 1

_{Thursday, May 28, 2015 12:24 PM ✅Answered}

Thanks very much Fares - your addition looks very good! I will give it a try in the next hour when I am finished with something else (pretty urgent) I am doing.

_{Thursday, May 28, 2015 11:55 AM}

Hallo Fares, thank you for your reply. It is quite helpful, but I have a large amount of columns and they are dynamic as well, so the number of columns can obviously vary and I won't know which column to delete until I trap it at run time. For example I have 57 columns in the 2D Array but I want to delete column 9, or even better (and which I really need) is to delete columns 9-14. Once I have found/know the left most column I want to delete that column and 4 or 5 more over to its right. Cany your code be adapted to fit the above problem? Or is there another way of doing it? I already have the 2D Array in an Array in this Format - arrCalculations[,] with thousands of rows and usually about 60 columns. (Of course this is easy in Excel which is where the array will eventually land, but the people I am working for want it all in C# for maintenance purposes as they don't have Excel programmers.) (Thank you very much for your help.)

_{Thursday, May 28, 2015 1:56 PM}

Fares - has worked wonderfully! Thanks very much! First class coding and help.