eigshow in Julia

eigshow.jl

A = [1 3; 4 2] / 4

blue = RGB(0., 0., 9.)
red = RGB(9., 0., 0.)

place(point) = (point .+ 1) ./ 4 .+ .25

drawpoints(points, c) =
[(context(place(points[:, i])..., 0.005, 0.005), fill(c), circle())
    for i = 1:size(points, 2)]

x=slider(0:.01:2π, value=0.)
xs=foldl(push!, Float64[0.1], x) # Accumilate previous values

display(x)

lift(xs) do xs
    xs = [cos(xs) sin(xs)]'
    Axs = A*xs
    compose(context(), [drawpoints(xs, blue),
        drawpoints(Axs, red)]...)
end

Version for 0.5:

using Compose, Interact, Colors, Reactive
A = [1 3; 4 2] / 4

blue = RGB(0., 0., 9.)
red = RGB(9., 0., 0.)

place(point) = (point .+ 1) ./ 4 .+ .25

drawpoints(points, c) =
[(context(place(points[:, i])..., 0.005, 0.005), fill(c), circle())
    for i = 1:size(points, 2)]
sl = slider(0:.01:2π, value = 0.)
x = signal(sl)
xs = map(push!, Signal(Float64[0.1]), x) # Accumilate previous values

display(sl)

map(xs) do xs
    xs = [cos(xs) sin(xs)]'
    Axs = A*xs
    
    compose(
        context(), [
        drawpoints(xs, blue);
        drawpoints(Axs, red)
    ]...)
end