Matrix.js

function Matrix (rows, columns) {
  if (rows instanceof Matrix) {
    const other = rows
    this.rows = other.rows
    this.columns = other.columns
    this.data = other.data.slice()
  } else {
    this.rows = rows
    this.columns = columns

    this.data = new Array(rows * columns)
    this.data.fill(0.0)
  }
}

Matrix.prototype.setIdentity = function () {
  for (let ii = 0; ii < this.rows; ++ii) {
    for (let jj = 0; jj < this.columns; ++jj) {
      if (ii === jj) {
        this.data[jj + ii * this.columns] = 1.0
      } else {
        this.data[jj + ii * this.columns] = 0.0
      }
    }
  }
}

Matrix.prototype.setElement = function (row, column, value) {
  this.data[column + row * this.columns] = value
}

Matrix.prototype.getElement = function (row, column) {
  return this.data[column + row * this.columns]
}

module.exports = Matrix