Bakhtiyor Bakhtiyor - 25 days ago 8
Javascript Question

Swap rows with columns (transposition) of a matrix in javascript

For instance I have a matrix like this:

|1 2 3|
|4 5 6|
|7 8 9|


and I need it to convert into a matrix like this:

|1 4 7|
|2 5 8|
|3 6 9|


What is the best and optimal way to achieve this goal?

Answer

see http://www.shamasis.net/2010/02/transpose-an-array-in-javascript-and-jquery

transpose = function(a) {

  // Calculate the width and height of the Array
  var w = a.length ? a.length : 0,
    h = a[0] instanceof Array ? a[0].length : 0;

  // In case it is a zero matrix, no transpose routine needed.
  if(h === 0 || w === 0) { return []; }

  /**
   * @var {Number} i Counter
   * @var {Number} j Counter
   * @var {Array} t Transposed data is stored in this array.
   */
  var i, j, t = [];

  // Loop through every item in the outer array (height)
  for(i=0; i<h; i++) {

    // Insert a new row (array)
    t[i] = [];

    // Loop through every item per item in outer array (width)
    for(j=0; j<w; j++) {

      // Save transposed data.
      t[i][j] = a[j][i];
    }
  }

  return t;
};

transpose([[1,2,3],[4,5,6],[7,8,9]]);