Playing with mathjs Matrices

index.js

// sudo npm install -g washington
// npm install mathjs
// washington index
var math      = require("mathjs")
math.type.Matrix.prototype.toString = function () {
  var string = "  ┌ "
  for (var i = 0; i < this.size()[1]; i ++)
    string += "  "
  string += "┐"
  this.forEach((function (value, index) {
    if (index[1] == 0)
      string += "\n  │ "
    string += value + " "
    if (index[1] + 1 == this.size()[1])
      string += "│"
  }).bind(this))
  string += "\n  └ "
  for (var i = 0; i < this.size()[1]; i ++)
    string += "  "
  string += "┘"
  return string
}
var arena     = require("washington")

arena("Multiplying something by the identity matrix", function () {
  var matrix    = math.matrix(
    [ [1, 1, 0], 
      [0, 0, 1], 
      [0, 1, 0] ] )

  var displace  = math.matrix(
    [ [0, 1, 0], 
      [0, 0, 1], 
      [1, 0, 0] ] )

  var identity  = math.eye(3)

  console.log("Original:")
  console.log(matrix.toString())

  console.log("Identity:")
  console.log(identity.toString())

  console.log("Displace:")
  console.log(displace.toString())

  console.log("Multiplication by identity:")
  console.log(math.multiply(matrix, identity).toString())  

  console.log("Multiplication by displace:")
  console.log(math.multiply(matrix, displace).toString())  

  arena("Determinant is " + math.det(identity))
})

arena("Displace one to the bottom", function () {
  var matrix = math.matrix([
    [4, 5, 3],
    [2, 4, 5],
    [8, 7, 4]
  ])

  console.log("Source:")
  console.log(matrix.toString())

  var displace = math.matrix([
    [0, 0, 1],
    [1, 0, 0],
    [0, 1, 0]
  ])

  console.log("One down:")
  console.log(displace.toString())

  arena("Displaced down:\n" +
        math.multiply(matrix, displace).toString())
})

arena("Lets try displacing a vector", function () {
  var vector = math.matrix([
    [1, 2, 3]
  ])

  console.log("Vector:")
  console.log(vector.toString())

  var displace = math.matrix([
    [0, 1, 0],
    [0, 0, 1],
    [1, 0, 0]
  ])

  console.log("Displace right:")
  console.log(displace.toString())

  console.log("Right:")
  console.log(math.multiply(vector, displace).toString())
})