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/
______________________________________________
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PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.
