[R] grImport symbols

[Paul Murrell]

Hi

baptiste auguie wrote:
> Dear list,
> 
> I have two questions regarding grid.symbols() in the grImport package.
> This package allows you to import a vector graphic in R, and
> grid.symbols() can be used to plot the resulting glyph at arbitrary
> locations in a grid viewport.
> 
> I have tried the code in the grImport vignette, which is most
> interesting, however I am stuck with two problems:
> 
> 1- Is there a possibility to create a Picture object directly from R
> without importing an external image, but rather specified as a regular
> grob/gTree, say. I would like to imitate my.symbols from
> TeachingDemos, but with grid.

You can directly create a Picture object.  An example is on slide 18 of 
http://www.stat.auckland.ac.nz/~paul/Talks/import.pdf

> 2- I could not figure out what the size argument in grid.symbols()
> does. The following example fails rather curiously.
> 
> petal.ps <- "%!PS
> newpath % start a new shape
> 0 0 moveto % move to a start location
> -5 10 lineto % line to a new location
> -10 20 10 20 5 10 curveto % curve to a third location
> 5 10 lineto % line to a fourth location
> closepath % connect back to the start location
> 0 setgray % set the drawing colour to black
> fill % fill the current shape"
> 
> cat(petal.ps, file="petal.ps")
> library(grImport)
> PostScriptTrace("petal.ps")
> petal <- readPicture("petal.ps.xml")
> 
> grid.symbols(petal, 1:10/10, 1:10/10, size=0.1) # OK
> 
> grid.symbols(petal, 1:10/10, 1:10/10, size = seq(0.01, 0.1,
> length=10)) # Warning and weird shapes

That's a bug in 'grImport' (could not cope with 'size' of length > 1).
A fix is winging its way to CRAN now.

Paul

> sessionInfo()
> R version 2.13.1 (2011-07-08)
> Platform: i386-apple-darwin9.8.0/i386 (32-bit)
> 
> locale:
> [1] en_GB.UTF-8/en_GB.UTF-8/C/C/en_GB.UTF-8/en_GB.UTF-8
> 
> attached base packages:
> [1] stats     graphics  grDevices utils     datasets  grid
> methods   base
> 
> other attached packages:
> [1] grImport_0.7-3 XML_3.4-0      ggplot2_0.8.9  proto_0.3-9.2  reshape_0.8.4
> [6] plyr_1.5.2
> 
> loaded via a namespace (and not attached):
> [1] tools_2.13.1
> 
> Best regards,
> 
> baptiste
> 
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-- 
Dr Paul Murrell
Department of Statistics
The University of Auckland
Private Bag 92019
Auckland
New Zealand
64 9 3737599 x85392
paul at stat.auckland.ac.nz
http://www.stat.auckland.ac.nz/~paul/