[R] how to compute the inverse percentile of a given observation w.r.t. a reference distribution
Dennis Murphy
djmuser at gmail.com
Wed May 25 23:50:23 CEST 2011
Hi:
On Wed, May 25, 2011 at 12:42 PM, rudi <rudi.strasser at gmail.com> wrote:
> Hi,
>
> can anyone help me to figure out how to compute the percentile of an
> individual observation with respect to a reference distribution.
>
> What I mean is. Let's assume I have a vector consisting of 10 numbers
> {3,5,8,1,9,5,4,3,5.5,7} and I want figure out what percentile the
> number 4.9 corresponds to. I failed to find any reference to such a
> function, although I would assume this must frequently be necessary.
The simple answer is, I believe,
x <- c(3,5,8,1,9,5,4,3,5.5,7)
plot(ecdf(x))
sum(x <= 4.9)/length(x)
[1] 0.4
This would correspond to the empirical cumulative distribution
function (ecdf) to which Jorge alluded.
HTH,
Dennis
>
> Thanks in advance for you help.
>
> /Rudi
>
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