[R] Superpose two QQ-plots (gamma distribution) with, lattice function qqmath()
Yvonnick Noel
yvonnick.noel at uhb.fr
Sat Jun 22 13:06:47 CEST 2013
David, Duncan,
> Hi
>
> Following on David's rate argument
>
> try (with modifications of pch and grid)
>
> rate <- 1/4
> shape = 8
> rate = c(rep(1/4,100),rep(1/3,100))
I don't think the problem is related to the rate argument, which can
well be vectorized, as is the case for a number of arguments in distrib
functions in R (note that you are redefining it as a vector above).
> x = rgamma(200,shape,rate)
> groups = gl(2,100,200,labels=LETTERS[1:2])
> dat = data.frame(x=x, gp=groups)
>
> qqmath(~ x, data = dat,
> groups = gp,
> pch = 20,
> type = c("p","g"),
> distribution = function(x) qgamma(x,shape,rate),
> panel = function(x,groups,...) {
> panel.qqmath(x,groups, ...)
> })
This works! Thank you very much (I had spent some time on that).
I now try to add a QQ-line but face a new problem. Only one line
appears, away from the points:
qqmath(~ x, data = dat,
groups = gp,
pch = 20,
type = c("p","g"),
distribution = function(x) qgamma(x,shape,rate),
panel = function(x,groups,...) {
panel.qqmath(x,groups, ...)
panel.qqmathline(x,groups,...)
})
Any hint?
Thanks a lot for your help,
Yvonnick
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