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 ? Regards Saptarshi Saptarshi Guha | sapsi@pobox.com | stat.purdue.edu/~sguha [[alternative HTML version deleted]]
Prof Brian Ripley
2007-Feb-06 21:05 UTC
[R] A question regarding cex and pch="." in lattice
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. 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. 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 | stat.purdue.edu/~sguha > > > [[alternative HTML version deleted]] > > ______________________________________________ > R-help at stat.math.ethz.ch mailing list > stat.ethz.ch/mailman/listinfo/r-help > PLEASE do read the posting guide 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, stats.ox.ac.uk/~ripley University of Oxford, Tel: +44 1865 272861 (self) 1 South Parks Road, +44 1865 272866 (PA) Oxford OX1 3TG, UK Fax: +44 1865 272595