[R] Highlighting points in a quantile plot for different values of a second column

[Peter Ehlers]

Saptarshi Guha wrote:
> Hello,
> I have the following data frame, using lattice and qqmath, how do I display the
> quantile plot (e.g distribution = qunif), but highlight the f==TRUE and f==FALSE
> differently?
> 
> library(lattice)
> pp <- function(n) ((1:n)-0.5)/n
> 
> x=data.frame(x=runif(20),f=sapply(runif(20),function(r) r>0.5))
> 
> I would like a single curve, the following example displays two curves.
> 
> qqmath(~x,groups=f,data=x,distribution=qunif,f.value=pp)
> 

Here's one way:

qqmath(~x, data=x, type='b',
   col=ifelse(x$f, 2, 4),
   pch=ifelse(x$f, 17, 19),cex=2)

  -Peter Ehlers

> 
> 
> Thank you
> Saptarshi
> 
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-- 
Peter Ehlers
University of Calgary