[R] create new variable: percentile value of variable in data frame

[Jonathan Beard]

Hi Stephan, thanks for your response.

It looks like the ecdf() works like it should.

I have a quick follow-up:

I didn't notice any discussion in the help documents of the methods
behind ecdf() and quantile(type=3) being equivalent.

It looks like the results produced by each method are consistent.

Any thoughts?

Again, thanks so much,

-Jon




On Fri, May 28, 2010 at 4:06 PM, Stephan Kolassa <Stephan.Kolassa at gmx.de> wrote:
> Hi Jon,
>
> does the empirical cumulative distribution function do what you want?
>
> dat$q.score <- ecdf(dat$score)(dat$score)
> ?ecdf
>
> HTH
> Stephan
>
>
> Jonathan Beard schrieb:
>>
>> Hello all,
>>
>> Thanks in advance for you attention.
>> I would like to generate a third value that represents the quantile
>> value of a variable in a data frame.
>>
>>
>> # generating data
>>
>> x <- as.matrix(seq(1:30))
>> y <- as.matrix(rnorm(30, 20, 7))
>> tmp1 <- cbind(x,y)
>> dat <- as.data.frame(tmp1)
>> colnames(dat) <- c("id", "score")
>> dat
>>
>> #  finding percentiles of "score"
>>
>> qs <- as.matrix(quantile(dat$score, type=3, probs = seq(0,1,.1)))
>> colnames(qs) <- c( "score")
>> qs
>>
>> #  is there a way to put the quantile value for a value of 'score'
>> into a new variable,
>> #  such that the new data frame would have three variables: id, score
>> and q.score?
>>
>> ##  running R version 2.8.1 (2008-12-22) on Vista
>>
>>
>> Thanks so much!
>>
>> -Jon
>>
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>>
>
>