You have a matrix
1 5 9
2 6 10
3 7 11
4 8 12
in column major order float matrixData[] = {1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12};
and you want to convert it to row major?
well, row major representation is the transpose of a column major representation.