Flipping a column in a matrix

Recently I have been making a Spectrum analyzer to keep myself busy. I have been trying to figure out how to flip 4 out of 7 columns in a matrix but can't seem to find the answer I am looking for.

Right now I have a 7 x 17 matrix and I would like to flip the 1,3,5,7 column so then I can prevent myself from having to rewire the data pins.

Schematic and code please. Read the forum guide in the sticky post, and follow it.

This should do it:

#define SIZE 17
#define COLUMNS 7
int thematrix[COLUMNS][SIZE];

void flip(int col)
{
  for (int i=0, j = SIZE-1; i< SIZE/2; i++, j--)
  {
    int temp = thematrix[col][i];
    thematrix[col][i] = thematrix[col][j];
    thematrix[col][j] = temp;
  }
}



void setup() {
  populate_the_matrix();
  flip(1-1);//first collumn has index zero
  flip(3-1);
  flip(5-1);
  flip(7-1);
}

void loop() {
  // put your main code here, to run repeatedly:

}