[R] how to make this qq plot in lattice and/or ggplot2

Deepayan Sarkar deepayan.sarkar at gmail.com
Sun Feb 8 08:18:28 CET 2009


On 2/7/09, Juliet Hannah <juliet.hannah at gmail.com> wrote:
> Hi Group,
>
>  Here is some data.
>
>  p <- runif(1000) # sample data
>  groups <- rep(c(1,2),each=500) #conditioning variable
>  mydata <- cbind(p,groups)
>  n <- length(p)
>  u <- (1:n)/(n + 1) # uniform distribution reference for qqplot
>  logp <- -log(p,base=10)
>  logu <- -log(u,base=10)
>  qqplot(logp,logu)
>
>  How can I make the above qqplot in lattice and/or ggplot2. The sample
>  is uniform, and I take -log10. In addition, I would like to use
>  the group variable to condition. I was not able to get the stat_qq
>  function in ggplot2 to work.

With lattice:

library(lattice)
qqmath(~ -log(p), data = as.data.frame(mydata), distribution = qexp)
qqmath(~ -log(p) | factor(groups), data = as.data.frame(mydata),
distribution = qexp)

-Deepayan



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