From: Paul Murrell<p.murr...@auckland.ac.nz>
Subject: Re: [R] need for speed on grid.rect
To: "Mikkel Grum"<mi2kelg...@yahoo.com>
Cc: "r-help@r-project.org"<r-help@r-project.org>
Date: Wednesday, October 20, 2010, 2:38 PM
Hi
I think the problem is that the Windows graphics device is
not great at
semitransparent colours. For example, your code runs
acceptably fast on
my Linux system.
If your goal is just a colour gradient, then you could
avoid using
semitransparency by calculating the colours yourself, for
example ...
library(colorspace)
finalColour<- rgb(coords(mixcolor(.5,
RGB(1, 0, 0),
RGB(t(col2rgb("lightblue"))/255))))
colourPalette<- colorRampPalette(c("lightblue",
finalColour))
... then just draw one set of rectangles ...
system.time(grid.rect(x = unit(rep(1:100, 200) ,
"native"),
y = unit(rep(1:200, each = 100),
"native"),
width = unit(1, "native"),
height = unit(1, "native"),
gp = gpar(col = NA,
fill =
colourPalette(20000))
))
... or even better, draw the gradient as a raster image
...
system.time(grid.raster(matrix(colourPalette(20000),
ncol=100, nrow=200, byrow=TRUE)))
... which is much faster again.
Paul
On 21/10/2010 6:10 a.m., Mikkel Grum wrote:
When I use grid.rect to print a multi-coloured grid,
it is
incredibly
slow compared to a single colour grid, or even a two colour
grid.
I've set out some simplified examples below. This is
something I run
literally thousands of times a day, so I would greatly
appreciate any
hints on how I might improve the speed???
library(grid)
pushViewport(viewport(
width = unit(100, "native"),
height = unit(100, "native"),
xscale = c(0, 100),
yscale = c(0, 100),
))
pushViewport(viewport(
x = unit(10, "native"),
y = unit(10, "native"),
width = unit(100, "native"),
height = unit(200, "native"),
xscale = c(0, 100),
yscale = c(0, 200),
just = c("left", "bottom"),
angle = 10))
system.time(grid.rect(x = unit(rep(1:100, 200) ,
"native"),
y = unit(rep(1:200, each = 100),
"native"),
width = unit(1, "native"),
height = unit(1, "native"),
gp = gpar(col = NA,
fill =
"lightblue")
))
system.time(grid.rect(x = unit(rep(1:100, 200) ,
"native"),
y = unit(rep(1:200, each = 100),
"native"),
width = unit(1, "native"),
height = unit(1, "native"),
gp = gpar(col = NA,
fill = rgb(1, 0,
0, 1:20000/40000))
))
My times for the two plots are:
user system elapsed
0.61 0.30
0.92
vs
user system elapsed
0.08
0.36 24.39
The time it takes to calculate the colours clearly
doesn't explain
the
difference:
system.time(rgb(1, 0, 0, 1:20000/20000))
user system elapsed
0
0 0
Even if I do a two coloured grid, it finishes as
quickly as the
single
coloured one, so my first interpretation is that the
function finds the
colours fairly quickly, e.g.
system.time(grid.rect(x = unit(rep(1:100, 200) ,
"native"),
y = unit(rep(1:200, each = 100),
"native"),
width = unit(1, "native"),
height = unit(1, "native"),
gp = gpar(col = NA,
fill =
c("lightblue", "red"))
))
user system elapsed
0.51 0.18
0.70
Best regards,
Mikkel
sessionInfo()
R version 2.12.0 (2010-10-15)
Platform: i386-pc-mingw32/i386 (32-bit)
locale:
[1] LC_COLLATE=English_Ireland.1252
LC_CTYPE=English_Ireland.1252
[3] LC_MONETARY=English_Ireland.1252 LC_NUMERIC=C
[5] LC_TIME=English_Ireland.1252
attached base packages:
[1] grid stats
graphics grDevices utils
datasets methods
[8] base
loaded via a namespace (and not attached):
[1] tools_2.12.0
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--
Dr Paul Murrell
Department of Statistics
The University of Auckland
Private Bag 92019
Auckland
New Zealand
64 9 3737599 x85392
p...@stat.auckland.ac.nz
http://www.stat.auckland.ac.nz/~paul/
