Arranging the columns of a matrix

Question

Arranging the columns of a matrix

My dilemma involves a matrix (or multidimensional array) filled with non-unique values, similar to this example:

var matrix = [
                [1, 3, 2, 4, 1],
                [2, 4, 1, 3, 2],
                [4, 3, 2, 1, 4]
             ]

I am in need of sorting one row within this matrix while ensuring that the other rows maintain their original order to preserve the column organization.

//Sorted matrix based on row 0
var sorted_matrix = [
                      [1, 1, 2, 3, 4],
                      [2, 2, 1, 4, 3],
                      [4, 4, 2, 3, 1]
                    ]

If possible, I am looking for a solution using lodash.

javascript sorting matrix lodash

Answer 1

Answer №1

To organize the data, create an array containing indices and sort it based on the values of matrix[0]. Then, generate a new array with the sorted elements.

var matrix = [[2, 4, 1, 3, 2], [1, 3, 2, 4, 1], [3, 2, 4, 1, 3]],
    indices = matrix[0].map((_, i) => i);

indices.sort((a, b) => matrix[0][a] - matrix[0][b]);

result = matrix.map(a => indices.map(i => a[i]));

console.log(result);

.as-console-wrapper { max-height: 100% !important; top: 0; }

Answer 2

To organize the data, create an array containing indices and sort it based on the values of matrix[0]. Then, generate a new array with the sorted elements.

var matrix = [[2, 4, 1, 3, 2], [1, 3, 2, 4, 1], [3, 2, 4, 1, 3]],
    indices = matrix[0].map((_, i) => i);

indices.sort((a, b) => matrix[0][a] - matrix[0][b]);

result = matrix.map(a => indices.map(i => a[i]));

console.log(result);

.as-console-wrapper { max-height: 100% !important; top: 0; }

Answer 3

Answer №2

To achieve matrix transposition using lodash, one approach is to utilize the zip function to transpose the matrix, followed by sorting it based on a specific row number using the sortBy function, and then finally re-transposing the matrix:

_.zip.apply(_, _.sortBy(_.zip.apply(_, matrix), row))

var matrix = [
    [1, 3, 2, 4, 1],
    [2, 4, 1, 3, 2],
    [4, 3, 2, 1, 4]
];
var row = 0;

result = _.zip.apply(_, _.sortBy(_.zip.apply(_, matrix), row));

console.log(result.join('\n'));

<script src="https://cdnjs.cloudflare.com/ajax/libs/lodash.js/4.16.4/lodash.min.js"></script>

Another way to write this operation is utilizing the rest parameter syntax:

_.zip( ..._.sortBy(_.zip( ...matrix), row));

Answer 4

To achieve matrix transposition using lodash, one approach is to utilize the zip function to transpose the matrix, followed by sorting it based on a specific row number using the sortBy function, and then finally re-transposing the matrix:

_.zip.apply(_, _.sortBy(_.zip.apply(_, matrix), row))

var matrix = [
    [1, 3, 2, 4, 1],
    [2, 4, 1, 3, 2],
    [4, 3, 2, 1, 4]
];
var row = 0;

result = _.zip.apply(_, _.sortBy(_.zip.apply(_, matrix), row));

console.log(result.join('\n'));

<script src="https://cdnjs.cloudflare.com/ajax/libs/lodash.js/4.16.4/lodash.min.js"></script>

Another way to write this operation is utilizing the rest parameter syntax:

_.zip( ..._.sortBy(_.zip( ...matrix), row));

Arranging the columns of a matrix

Answer №1

Answer №2

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