[R] Function to assign quantiles?

[hadley wickham]

On 2/16/07, Frank E Harrell Jr <f.harrell at vanderbilt.edu> wrote:
> Marc Schwartz wrote:
> > On Thu, 2007-02-15 at 17:50 -0500, Talbot Katz wrote:
> >> Hi.
> >>
> >> If I call the quantiles function as follows:
> >>
> >> qvec = quantiles(dvals,probs=seq(0,1,0.1))
> >>
> >> the results will return a vector something like the following example:
> >>
> >>       0%    10%    20%    30%     40%     50%    60%    70%      80%     90%
> >>      100%
> >>     56.0   137.3   238.4   317.9   495.8   568.5   807.4  1207.7  1713.0
> >> 2951.1  8703.0
> >>
> >> Now I want to assign the deciles, 1 - 10, to each observation, so, in the
> >> above example, if dvals[322] = 256, I want to assign qvals[322] = 3, and if
> >> dvals[7216] = 1083, I want qvals[7216] = 7, etc.  I would think there would
> >> be a function, or some very quick code to do that, but I couldn't find it.
> >>
> >> Here's what I have now.  It works, but I figure there must be a better way:
> >>
> >> asdc <- function(q){max(1,which(qvec<q))}
> >> qvals = apply(matrix(dvals,nrow=1),2,asdc)
> >>
> >>
> >> Any suggestions?  Thanks!
> >
> > Take a look at ?cut and use the output of quantile() to define the
> > 'breaks' argument:
> >
> > x <- rnorm(100)
> >
> >> cut(x, breaks = quantile(x, probs = seq(0, 1, 0.1)),
> >       include.lowest = TRUE, labels = 1:10)
> >   [1] 2  1  9  10 9  3  1  7  5  2  4  1  10 8  4  10 9  9  5  3  5  8
> >  [23] 6  9  7  1  10 1  10 9  3  3  9  3  5  5  6  4  8  10 6  2  2  8
> >  [45] 6  3  6  9  1  4  7  10 8  7  5  3  1  10 2  1  7  8  8  2  8  8
> >  [67] 3  10 4  6  5  1  4  6  4  4  5  9  9  7  2  8  2  5  1  3  7  6
> >  [89] 4  6  4  6  2  7  2  10 7  3  5  7
> > Levels: 1 2 3 4 5 6 7 8 9 10
> >
> >
> > HTH,
> >
> > Marc Schwartz
> >
> > ______________________________________________
> > R-help at stat.math.ethz.ch 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.
>
> Or see the cut2 function in the Hmisc package

Or the chop function in ggplot package - it's a common problem.

Hadley