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# Define the function
ggd.qqplot = function(pvector, main=NULL, ...) {
o = -log10(sort(pvector,decreasing=F))
e = -log10( 1:length(o)/length(o) )
plot(e,o,pch=19,cex=1, main=main, ...,
xlab=expression(Expected~~-log[10](italic(p))),
ylab=expression(Observed~~-log[10](italic(p))),
xlim=c(0,max(e)), ylim=c(0,max(e)))
lines(e,e,col="red")
}
#Generate some fake data that deviates from the null
set.seed(42)
pvalues=runif(10000)
pvalues[sample(10000,10)]=pvalues[sample(10000,10)]/5000
# pvalues is a numeric vector
pvalues[1:10]
# Using the ggd.qqplot() function
ggd.qqplot(pvalues)
# Add a title
ggd.qqplot(pvalues, "QQ-plot of p-values using ggd.qqplot")
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