Tech Tips

とある統計のアルゴリズムの動きを視覚的に確認したいがために、
それの全段階としてCoffeeScriptとHTML5のCanvasでアニメーション処理を書いてみた。 まずmain.coffee。

Point2D = require('../src/point2d').Point2D

main = ()->
    canvas = document.getElementById('canvas')
    context = canvas.getContext('2d')

    num_points = 9
    labels = ["abc", "bcd", "cde", "def", "efg", "fgh", "ghi", "hij", "ijk", "jkl"]
    points = []
    for i in [0..num_points]
        x = canvas.width /2 + Math.floor(Math.random() * 200) - 100
        y = canvas.height /2 + Math.floor(Math.random() * 200) - 100
        vx = Math.random() * 5.0 - 2.5
        vy = Math.random() * 5.0 - 2.5

        points.push new Point2D(x, y, 10, vx, vy, labels[i], canvas.width, canvas.height, context)
        points[i].draw()

    mainloop = ()->
        context.save()
        context.beginPath()
        context.clearRect(0, 0, canvas.width, canvas.height)
        context.restore()

        for i in [0..num_points]
            points[i].update_position()
            points[i].reflect()
            points[i].draw()

        setTimeout(mainloop, 30)

    mainloop()

window.onload = main

次に、2次元のデータ点を表現するpoint2d.coffee。

class Point2D
    constructor: (x, y, r, vx, vy, label, wnd_width, wnd_height, context) ->
        @x = x
        @y = y
        @r = r
        @vx = vx
        @vy = vy
        @label = label
        @wnd_width = wnd_width
        @wnd_height = wnd_height
        @context = context

    update_position: ->
        @x += @vx
        @y += @vy

    reflect: ->
        if @x - @r < 0
            @x = @r
            @vx *= -1.0

        if @x + @r > @wnd_width
            @x = @wnd_width - @r
            @vx *= -1.0

        if @y - @r < 0
            @y = @r
            @vy *= -1.0

        if @y + @r > @wnd_height
            @y = @wnd_height - @r
            @vy *= -1.0

    draw: ->
        @context.beginPath()
        @context.strokeStyle = '#00F'
        @context.fillStyle = '#00F'
        @context.arc(@x, @y, @r, 0, Math.PI * 2, false)
        @context.fill()
        @context.stroke()
        @context.restore()

        @context.beginPath()
        @context.font = "18px 'MS Pゴシック'"
        @context.fillStyle = "blue"
        @context.fillText(@label, @x, @y-@r)
        @context.restore()

exports.Point2D = Point2D

無駄にテストコードも書いてしまった。
ちなみにjasmine-nodeを使っております。

Point2D = require('../src/point2d').Point2D

describe "Point2D", ->
    p1 = undefined
    p2 = undefined
    p3 = undefined
    p4 = undefined
    p5 = undefined
    p6 = undefined

    beforeEach ->
        p1 = new Point2D(0, 0, 0, 0, 0, "", 0, 0, undefined)
        p2 = new Point2D(100, 200, 30, 2.0, 2.0, "test", 640, 480, undefined)
        p3 = new Point2D(5, 200, 30, 2.0, 2.0, "test", 640, 480, undefined)
        p4 = new Point2D(630, 200, 30, 2.0, 2.0, "test", 640, 480, undefined)
        p5 = new Point2D(100, 10, 30, 2.0, 2.0, "test", 640, 480, undefined)
        p6 = new Point2D(100, 470, 30, 2.0, 2.0, "test", 640, 480, undefined)

    it "should be x and y axis value are 0", ->
        expect(p1.x).toEqual 0
        expect(p1.y).toEqual 0
        expect(p1.r).toEqual 0
        expect(p1.vx).toEqual 0
        expect(p1.vy).toEqual 0
        expect(p1.wnd_width).toEqual 0
        expect(p1.wnd_height).toEqual 0
        expect(p1.label).toEqual ""

    it "should be x and y axis value are 5, 10", ->
        expect(p2.x).toEqual 100
        expect(p2.y).toEqual 200
        expect(p2.r).toEqual 30
        expect(p2.vx).toEqual 2.0
        expect(p2.vy).toEqual 2.0
        expect(p2.wnd_width).toEqual 640
        expect(p2.wnd_height).toEqual 480
        expect(p2.label).toEqual "test"

    it "should add velocity for x and y to 102.0 and 202.0", ->
        p2.update_position()
        expect(p2.x).toEqual 102.0
        expect(p2.y).toEqual 202.0

    it "should reflect with left side", ->
        p3.reflect()
        expect(p3.x).toEqual 30
        expect(p3.vx).toEqual -2.0

    it "should reflect with right side", ->
        p4.reflect()
        expect(p4.x).toEqual 610
        expect(p4.vx).toEqual -2.0

    it "should reflect with left side", ->
        p5.reflect()
        expect(p5.y).toEqual 30
        expect(p5.vy).toEqual -2.0

    it "should reflect with left side", ->
        p6.reflect()
        expect(p6.y).toEqual 450
        expect(p6.vy).toEqual -2.0

ここまでの実行結果はこんな感じ。
さて、後は多次元尺度構成法のアルゴリズムを乗っければ完成だ。I want to watch a statistical algorithm’s behavior,
so I wrote animation program with Coffee Script and Canvas on HTML5 before it.