R help - Feb 2009 - how to make this qq plot in lattice and/or ggplot2

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.

Thanks for your time.

Regards,

Juliet

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

On Sat, Feb 7, 2009 at 9:25 PM, 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 ggplot2:

qplot(sample = -log(p), distribution = qexp)
qplot(sample = -log(p), distribution = qexp, colour = factor(group))

However, the major caveat is that this doesn't work in the released
version, but does in the development version, which I can send you off
list if you tell me what operating system you use.

Hadley

-- 
http://had.co.nz/