[R] "normal probability plot" with a percentile scale?

Peter Dalgaard BSA p.dalgaard at biostat.ku.dk
Wed May 1 10:11:46 CEST 2002

```Russell Senior <seniorr at aracnet.com> writes:

> I'd like to generate some plots like you'd see on the old "normal
> probability graph paper", like the first plot in:
>
>   <http://www.itl.nist.gov/div898/handbook/eda/section3/normprpl.htm>
>
> except the horizontal scale would have 1%, 5%, 25%, 50%, 75%, 95%,
> 99%, or similar quantiles, with associated tick/grid lines.  [still
> hunting around for a good example...] something like these, but with
> the probability along the horizontal axis:

This'll be close:

x <- rnorm(100)
pp <- c(.01, .05, .25, .50, .75, .95,.99)
qq <- qnorm(pp)
qqnorm(x,axes=F)
axis(2)
axis(1,at=qq,labels=pp)
box()

For smaller samples, you may need to throw in an xlim=range(qq)
argument.

--
O__  ---- Peter Dalgaard             Blegdamsvej 3
c/ /'_ --- Dept. of Biostatistics     2200 Cph. N
(*) \(*) -- University of Copenhagen   Denmark      Ph: (+45) 35327918
~~~~~~~~~~ - (p.dalgaard at biostat.ku.dk)             FAX: (+45) 35327907
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```