Sinus plotter visualization (animGIF)

first.R

# install.packages("animation")

# A sinus plotter in R just to demo animations.

library(animation)

n.frames = 200
max.t = 60
max.i = 60
all.i = 1:max.i
trail.dt = 3    # length of trail timewise

draw.phase = function(frame.idx, alpha = 1) {
  colors = rgb(1 - all.i / max.i, 1 - all.i / max.i, all.i / max.i, alpha)
  t = (frame.idx - 1) / (n.frames - 1) * max.t

  t.all = t + (0:(max.i - 1)) / (max.i - 1) * trail.dt

  x = sin(t.all * 15 / 60 * pi * 2)
  y = cos(t.all * 28 / 60 * pi * 2)
  points(x, y, col = colors)
}

saveGIF({
  dec.frame.index = function(frame.idx, by = 1) {
    return((frame.idx - by) %% n.frames)
  }

  ani.options(nmax = n.frames)
  for(frame.idx in 1:n.frames) {
    plot(x = c(), xlim = c(-1.5, 1.5), ylim = c(-1.5, 1.5),
         axes = FALSE, xlab = "", ylab = "",
         main = "Once there was a sinus plotter ...")

    draw.phase(dec.frame.index(frame.idx, 2), alpha = 0.25)
    draw.phase(dec.frame.index(frame.idx, 1), alpha = 0.5)
    draw.phase(frame.idx, alpha = 1)
  }},
  interval = 0.05, movie.name = "sinus_plotter.gif",
  ani.width = 600, ani.height = 400)