# [R] Extracting values from a ecdf (empirical cumulative distribution function) curve

Duncan Mackay dulcalma at bigpond.com
Fri Nov 1 03:40:14 CET 2013

```Hi

There is a print method for ecdf

So print(f) should give you an idea of what is going on

See ?ecdf

HTH

Duncan

Duncan Mackay
Department of Agronomy and Soil Science
University of New England
Armidale NSW 2351
Email: home: mackay at northnet.com.au

-----Original Message-----
From: r-help-bounces at r-project.org [mailto:r-help-bounces at r-project.org] On
Behalf Of Manoranjan Muthusamy
Sent: Friday, 1 November 2013 11:18
Cc: r-help at r-project.org
Subject: Re: [R] Extracting values from a ecdf (empirical cumulative
distribution function) curve

Thank you, Barradas. It works when finding y, but when I tried to find x
using interpolation for a known y it gives 'NA' (for whatever y value). I
couldn't find out the reason. Any help is really appreciated.

Thanks,
Mano

On Thu, Oct 31, 2013 at 10:53 PM, Rui Barradas <ruipbarradas at sapo.pt> wrote:

> Hello,
>
> As for the problem of finding y given the ecdf and x, it's very easy,
> just use the ecdf:
>
> f <- ecdf(rnorm(100))
>
> x <- rnorm(10)
> y <- f(x)
>
> If you want to get the x corresponding to given y, use linear
> interpolation.
>
> inv_ecdf <- function(f){
>         x <- environment(f)\$x
>         y <- environment(f)\$y
>         approxfun(y, x)
> }
>
> g <- inv_ecdf(f)
> g(0.5)
>
>
> Hope this helps,
>
>
> Em 31-10-2013 12:25, Manoranjan Muthusamy escreveu:
>
>> Hi R users,
>>
>> I am a new user, still learning basics of R. Is there anyway to
>> extract y (or x) value for a known x (or y) value from ecdf
>> (empirical cumulative distribution function) curve?
>>
>> Thanks in advance.
>> Mano.
>>
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>>
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>>
>>

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