[R] A question regarding cex and pch="." in lattice

[Saptarshi Guha]

On Feb 6, 2007, at 4:05 PM, Prof Brian Ripley wrote:

> How do you know the points are not being plotted?
>
> All you can tell is that your graphics card / monitor / X11 driver  
> is not
> displaying them, not at all the same thing.
>

Yes, that is what I meant but I suppose I conveyed it wrongly.



> My guess is that the rectangle is being displayed only if the  
> differences in its discretized x and y coordinates are both  
> positive.  R tries hard to ensure that pch='.', cex=1 does always  
> display a point, but not for smaller cex.

This could be the case.
Thanks
Saptarshi


>
> On Tue, 6 Feb 2007, Saptarshi Guha wrote:
>
>> Hello,
>> 	I'm using lattice and opened an X11 device with the following call
>> 	X11(width=5,height=5,pointsize=1)
>> 	I then ran the following code
>>
>> 	library(lattice)
>> 	x<-rnorm(30,sd=2)
>> 	y<-runif(30)
>> 	xyplot(y~x,pch=".",col="black",cex=1)
>>
>> 	If i remove "cex=1", not all the points are plotted. From ?X11, i
>> read,"pch='.' with cex=1 corresponds to a rectangle of sides the
>> larger of one pixel and 0.01 inch"
>>
>> 	By way of information, i'm using a Dell 30", where the the pixel
>> pitch is 0.250mm(0.0098 inch).
>>
>> 	My question, why is that some of the points are not being plotted
>> when remove cex=1 ?
>
> The default cex for this plot is 0.8. See trellis.par.get 
> ("plot.symbol").
>
>> 	Regards
>> 	Saptarshi
>>
>> Saptarshi Guha | sapsi at pobox.com | http://www.stat.purdue.edu/~sguha
>>
>>
>> 	[[alternative HTML version deleted]]
>>
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>
> -- 
> 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)
> 1 South Parks Road,                     +44 1865 272866 (PA)
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