[R] cex multiplier not exact

[Prof Brian Ripley]

On Mon, 24 Oct 2011, Uwe Ligges wrote:

>
>
> On 23.10.2011 22:33, Ali Tofigh wrote:
>> Hi,
>> 
>> When I plot text and use cex to change the text size, I notice that the cex
>> multiplier is not exact. It looks as if the real size of text can take only
>> certain discrete values. Is there a workaround to get text to follow the 
>> cex
>> value more closely, or at least to be able to figure out what the real cex 
>> value
>> will be?
>
> Typically this is multiplied by the default pointsize of the current device 
> and rounded to an integer - the resulting pointsize that you see with your 
> code.
>
> If you want to know it absolute precisely: This may even depend on the device 
> and I think you will have to read the source code in order to find out how it 
> is actually implemented for your current device (which you have not even 
> stated).

It may be in the help for that unstated device (the help for windows() 
says that it is rounded to bigpoints), and in some cases the rounding 
is in the OS services (it is for the X11() device, for example) and 
hence very hard to know precisely.

Oh, and the cex for text and for symbols (pch = 0:25) may not work the 
same way.

>
> Uwe Ligges
>
>
>> 
>> Here is an example that illustrates the problem:
>> 
>> cex<- seq(0.5, 1, 0.01)
>> x<- 0.05
>> y<- (1:length(cex))/length(cex)
>> labels<- paste("XXXXXX", cex)
>> plot.new()
>> text(x=x, y=y, labels=labels, pos=4, cex=cex)
>> 
>> /Ali
>> 
>> ______________________________________________
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>> and provide commented, minimal, self-contained, reproducible code.
>
> ______________________________________________
> R-help at 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.
>

-- 
Brian D. Ripley,                  ripley at stats.ox.ac.uk
Professor of Applied Statistics,  http://www.stats.ox.ac.uk/~ripley/
University of Oxford,             Tel:  +44 1865 272861 (self)
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