Transposing a 2D-Array in JavaScript

Transposing a 2D-array in JavaScript

output = array[0].map((_, colIndex) => array.map(row => row[colIndex]));

map calls a provided callback function once for each element in an array, in order, and constructs a new array from the results. callback is invoked only for indexes of the array which have assigned values; it is not invoked for indexes which have been deleted or which have never been assigned values.

callback is invoked with three arguments: the value of the element, the index of the element, and the Array object being traversed. [source]

how to transpose 2d array using javascript

const testArray = [["SFT_DEA_LXD", 115494.1],
["SFT_ISA_LXD", 10082.31]];

const newArray = [];
const newArray1 = [];
testArray.forEach(item => {
    newArray.push(item[0]);
    newArray1.push(item[1]); 
});
const result = [newArray, newArray1];

Transpose a two dimensional Array with one row and many columns into a two dimensional array with many rows and one column

I guess your goal as follows.

• From var dataArr = shrinkLog.getRange(2,3,1,shrinkLog.getLastColumn()).getValues(), you want to retrieve the result from [[data1, data2, data3,,,]] to [[data1], [data2], [data3],,,]].

In your case, shrinkLog.getRange(2,3,1,shrinkLog.getLastColumn()).getValues() returns [[data1, data2, data3,,,]]. So when your goal is achieved with map, the modified script is as follows.

Sample script:

var dataArr = shrinkLog.getRange(2,3,1,shrinkLog.getLastColumn()).getValues()[0].map(c => [c]);

Note:

• In this case, please enable V8 runtime.

Reference:

• map()

Transposing JavaScript Multi D arrays

You can so something like this, using map and for loop. But honestly I find this unnecessary. You could just do this from the get go in your loop. instead of pushing to row, you could try:

row[0][timeframes[t]] = "that long thing you have there"

const arr = [
  [{
      "ticker": "JPM"
    },
    {
      "move": 0.01405944118170499
    },
    {
      "move": 0.0337445573294628
    },
    {
      "move": 0.1692882281117576
    },
    {
      "move": 0.07636499188035195
    },
    {
      "move": 0.8151371865267423
    },
    {
      "move": 0.4537049320855997
    }
  ],
  [{
      "ticker": "C"
    },
    {
      "move": -0.01295986622073586
    },
    {
      "move": 0.002689694224235595
    },
    {
      "move": 0.05544868117343582
    },
    {
      "move": -0.0457495911125243
    },
    {
      "move": 0.7837535634777528
    },
    {
      "move": 0.05665004788714745
    }
  ],
  [{
      "ticker": "C"
    },
    {
      "move": -0.01295986622073586
    },
    {
      "move": 0.002689694224235595
    },
    {
      "move": 0.05544868117343582
    },
    {
      "move": -0.0457495911125243
    },
    {
      "move": 0.7837535634777528
    },
    {
      "move": 0.05665004788714745
    }
  ],

]

const flatObj = (arr) => {
  const flatObject = {};
  const keys = ["ticker", "5", "10", "90", "120", "250", "500"]
  for (let i = 0; i < arr.length; i++) {
    for (const property in arr[i]) {
      flatObject[keys[i]] = arr[i][property];
    }
  };
  return flatObject;
}

const result = arr.map(ar => flatObj(ar))

console.log(result)

Transposing variable size array in javascript?

You could transpose the array by using arrays with the length of the outer array as length for every line.

var array = [[1, 2], [], [3], [4, 5, 6], [,,7]],

    result = array.reduce((r, a, i, { length }) => {

        a.forEach((v, j) => {

            r[j] = r[j] || new Array(length).fill('');

            r[j][i] = v;

        });

        return r;

    }, []);

    

console.log(result);

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

See article: Transpose An Array In JavaScript and jQuery

function transpose(a) {

  // Calculate the width and height of the Array

  var w = a.length || 0;

  var 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;

}

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

How to transpose 2D square matrix stored as 1D array in Javascript

You could take the length for the dimension of the array and map items on a specific index for a new array.

var array = [1 ,2, 3, 4, 5, 6, 7, 8, 9],

    n = Math.sqrt(array.length),

    transposed = array.map((_, i, a) => a[(i % n) * n + Math.floor(i / n)]);

    

console.log(transposed.join(' '));

Transpose irregular matrix in JavaScript

There are a lot of ways to solve this (as other answers demonstrate). Here's how I'd do it, as it minimizes the number of times we iterate over the data.

const data = [

  [undefined, undefined],

  [1, 2, 3, 4],

  [1, 2],

  [undefined, undefined, undefined],

  [1, 2, 3, 4, 5, 6],

];

// get the length of the longest array

const maxLen = data.reduce((max, {length}) => Math.max(max, length), 0);

// make a new set of arrays

const result = Array.from({ length: maxLen }, (_, i) => data.map(col => col[i]));

console.log(result);

---

Related Topics