[R] Superpose two QQ-plots (gamma distribution) with lattice function qqmath()
Yvonnick Noel
yvonnick.noel at uhb.fr
Fri Jun 21 16:55:06 CEST 2013
Hello,
I am trying to superpose on a single panel two QQ plots with the lattice
qqmath function.
Here is a reproducible example of the problem I am facing:
# Generate data
shape = 8
rate = c(rep(1/4,100),rep(1/3,100))
x = rgamma(200,shape,rate)
groups = gl(2,100,200,labels=LETTERS[1:2])
# Plot
qqmath(~x,groups=groups,panel = "panel.superpose",
distribution = function(x) qgamma(x,shape,rate),
panel.groups = function(x,subscripts,...) {
panel.qqmath(x,shape=shape,rate=rate[subscripts],...)
panel.qqmathline(x,shape=shape,rate=rate[subscripts],...)
})
Both data series seem to be reproduced twice, somewhat rescaled.
I don't understand what this mean.
What am I doing wrong?
Thanks a lot for your help,
Yvonnick Noel
University of Brittany, Rennes
Dpt. of Psychology
France
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