R help - Aug 2011 - how to get the percentile of a number in a vector

I'm familiar with the quantile() command, but what if I have a specific
   number that I want to know its location in a vector? I know that in known
   distributions, (for example the normal distribution), there is pnorm and
   qnorm, but how can I do it with unknown vector?


   thanks in advance
     _________________________________________________________________

   Walla! Mail - [1]Get your free unlimited mail today

References

   1. http://www.walla.co.il/

On Aug 2, 2011, at 10:14 AM, ????? ???????? wrote:
>
>   I'm familiar with the quantile() command, but what if I have a  
> specific
>   number that I want to know its location in a vector? I know that  
> in known
>   distributions, (for example the normal distribution), there is  
> pnorm and
>   qnorm, but how can I do it with unknown vector?
?ecdf

-- 

David Winsemius, MD
West Hartford, CT

Would this work for you?

if you want to know where the i-th element falls percentage-wise in the
distribution of a vector:

sum(x <= x[i])/length(x)

This could be turned into a function:

pEmpirical <- function(i,x) {
    if (length(i) > 1) return(apply(as.matrix(i), 1, pEmpirical,x))
    r = sum(x <= x[i])/length(x)
    return(r)
}

Michael Weylandt

2011/8/2 ראובן אברמוביץ <gantkant@walla.com>
>
>   I'm familiar with the quantile() command, but what if I have a
specific
>   number that I want to know its location in a vector? I know that in known
>   distributions, (for example the normal distribution), there is pnorm and
>   qnorm, but how can I do it with unknown vector?
>
>
>   thanks in advance
>     _________________________________________________________________
>
>   Walla! Mail - [1]Get your free unlimited mail today
>
> References
>
>   1. http://www.walla.co.il/
>
> ______________________________________________
> R-help@r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide
> http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
>
>
	[[alternative HTML version deleted]]

Does this help?

x <- c(3, 8, 5, 2, 9, 33, 21)

# the 43rd percentile
quantile(x, 0.43)

# the proportion of the distribution that is less than 7
mean(x<7)

Jean


`·.,,  ><(((?>   `·.,,  ><(((?>   `·.,,  ><(((?>

Jean V. Adams
Statistician
U.S. Geological Survey
Great Lakes Science Center
223 East Steinfest Road
Antigo, WI 54409  USA



From:
øàåáï àáøîåáéõ <gantkant@walla.com>
To:
<r-help@r-project.org>
Date:
08/02/2011 10:51 AM
Subject:
[R] how to get the percentile of a number in  a vector
Sent by:
r-help-bounces@r-project.org




   I'm familiar with the quantile() command, but what if I have a specific
   number that I want to know its location in a vector? I know that in 
known
   distributions, (for example the normal distribution), there is pnorm 
and
   qnorm, but how can I do it with unknown vector?


   thanks in advance
     _________________________________________________________________

   Walla! Mail - [1]Get your free unlimited mail today

References

   1. http://www.walla.co.il/
______________________________________________
R-help@r-project.org mailing list
https://stat.ethz.ch/mailman/listinfo/r-help
PLEASE do read the posting guide 
http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.




	[[alternative HTML version deleted]]