mathjs/src/function/matrix/row.js

'use strict'

const clone = require('../../utils/object').clone
const validateIndex = require('../../utils/array').validateIndex

function factory (type, config, load, typed) {
  const MatrixIndex = load(require('../../type/matrix/MatrixIndex'))
  const matrix = load(require('../../type/matrix/function/matrix'))
  const range = load(require('./range'))

  /**
   * Return a row from a Matrix.
   *
   * Syntax:
   *
   *     math.row(value, index)
   *
   * Example:
   *
   *     // get a row
   *     const d = [[1, 2], [3, 4]]
   *     math.row(d, 1) // returns [3, 4]
   *
   * See also:
   *
   *     column
   *
   * @param {Array | Matrix } value   An array or matrix
   * @param {number} row              The index of the row
   * @return {Array | Matrix}         The retrieved row
   */
  const row = typed('row', {
    'Matrix, number': _row,

    'Array, number': function (value, row) {
      return _row(matrix(clone(value)), row).valueOf()
    }
  })

  row.toTex = undefined // use default template

  return row

  /**
   * Retrieve a row of a matrix
   * @param {Matrix } value  A matrix
   * @param {number} row     The index of the row
   * @return {Matrix}        The retrieved row
   */
  function _row (value, row) {
    // check dimensions
    if (value.size().length !== 2) {
      throw new Error('Only two dimensional matrix is supported')
    }

    validateIndex(row, value.size()[0])

    const columnRange = range(0, value.size()[1])
    const index = new MatrixIndex(row, columnRange)
    return value.subset(index)
  }
}

exports.name = 'row'
exports.factory = factory