Hi Paul
Thanks ever so much for this. This should help tremendously. My only reason for
using semi-transparent colours was not knowing how to use colorRampPalette. I'm
really just looking at white-to-somecolour gradients. My examples weren't meant
to be written one on top of the other.
Unlike in the examples, my real-life grids are irregular, with uneven distances
between rows, so grid.raster probably isn't an option.
Also, in real-life I'm writing the plots to png and pdf files. It was on the
png files that I noticed the problem, because these files involve much more
data than the pdfs. I'm not sure to what extent the Windows graphics drivers
affects the png and pdf drivers?
Mikkel
--- On Wed, 10/20/10, Paul Murrell <p.murr...@auckland.ac.nz> wrote:
> 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
> >
> > ______________________________________________
> > R-help@r-project.org
> mailing list
> > https://stat.ethz.ch/mailman/listinfo/r-help
> > PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
> > and provide commented, minimal, self-contained,
> reproducible code.
>
> --
> 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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