[R] tip: large plots

[Sarah Goslee]

Hi all,

I'm working with a bunch of large graphs, and stumbled across
something useful. Probably many of you know this, but I didn't and so
others might benefit.

Using pch="." speeds up plotting considerably over using symbols.

> x <- runif(1000000)
> y <- runif(1000000)
> system.time(plot(x, y, pch="."))
   user  system elapsed
  1.042   0.030   1.077
> system.time(plot(x, y))
   user  system elapsed
 37.865   0.033  38.122

If you have enough points, the result is also more legible.

Choice of which pch symbol makes a difference too, the default pch=1 being
the slowest of what I tried, but "." is by far the speediest.

> system.time(plot(x, y, pch=0))
   user  system elapsed
 11.191   0.011  11.270
> system.time(plot(x, y, pch=1))
   user  system elapsed
 38.024   0.008  38.245
> system.time(plot(x, y, pch=2))
   user  system elapsed
 14.140   0.027  14.270
> system.time(plot(x, y, pch=3))
   user  system elapsed
 15.696   0.011  15.799
> system.time(plot(x, y, pch=4))
   user  system elapsed
 18.770   0.007  18.888

This is a vanilla R session, 2.13.1 for x86_64-redhat-linux-gnu. I
haven't tried it on any other OS, but it's making my life a lot
smoother right now.

Sarah

-- 
Sarah Goslee
http://www.functionaldiversity.org