[R] Order of factor levels

[Thierry Onkelinx]

Here's a solution with dplyr

my_cut <- function(x){
  breaks <- quantile(x, seq(0, 1, by = 0.1))
  y <- cut(x, breaks = breaks, include.lowest = TRUE)
  levels(y) <- paste(head(letters, length(breaks) - 1), levels(y), sep = ":
")
  return(y)
}

library(dplyr)
mutate_each(df, funs = funs(my_cut))


ir. Thierry Onkelinx
Instituut voor natuur- en bosonderzoek / Research Institute for Nature and
Forest
team Biometrie & Kwaliteitszorg / team Biometrics & Quality Assurance
Kliniekstraat 25
1070 Anderlecht
Belgium

To call in the statistician after the experiment is done may be no more
than asking him to perform a post-mortem examination: he may be able to say
what the experiment died of. ~ Sir Ronald Aylmer Fisher
The plural of anecdote is not data. ~ Roger Brinner
The combination of some data and an aching desire for an answer does not
ensure that a reasonable answer can be extracted from a given body of data.
~ John Tukey

2016-01-11 20:34 GMT+01:00 William Dunlap via R-help <r-help op r-project.org>:

> Don't use vapply() here - use lapply() instead and then leave cut's output
> alone.
>
> vapply() will combine its outputs to create a character matrix and
> data.frame will pull apart the character matrix into its columns.  Skipping
> the matrix intermediary solves
> lots of issues.
>
> Bill Dunlap
> TIBCO Software
> wdunlap tibco.com
>
> On Mon, Jan 11, 2016 at 11:24 AM, Guelman, Leo <leo.guelman op rbc.com>
> wrote:
>
> > Dear list,
> >
> > What is a better way relative to the one below to keep the order of
> factor
> > levels created from cut()? Notice, I'm simply pasting letters to levels
> > before converting to character so to keep the desired order of levels.
> This
> > is not very elegant... I'm converting to character so I can call the
> helper
> > fun with vapply() from the main fun.
> >
> > Removing this line of code "  levels(xc) <- paste(letters[1:nlevels(xc)],
> > levels(xc), sep=":")" would result in factor levels that are not ordered
> > according to x1.
> >
> > set.seed(1)
> > df <- data.frame(x1 = rnorm(1000), x2 = rnorm(1000))
> >
> > main_fun <- function(data) {
> >   data.frame(vapply(data, helper_fun, character(nrow(df))))
> > }
> >
> > helper_fun <- function(x) {
> >   xc <-  cut(x, breaks = unique(quantile(x, seq(0, 1, 1/10), na.rm =
> > TRUE)),
> >              include.lowest = TRUE)
> >   levels(xc) <- paste(letters[1:nlevels(xc)], levels(xc), sep=":")
> >   as.character(xc)
> >
> > }
> >
> >
> > res <- main_fun(df)
> > levels(res$x1)
> > levels(res$x1)
> >  [1] "a:[-3.01,-1.34]"    "b:(-1.34,-0.882]"   "c:(-0.882,-0.511]"
> > "d:(-0.511,-0.296]"  "e:(-0.296,-0.0353]"
> >  [6] "f:(-0.0353,0.245]"  "g:(0.245,0.536]"    "h:(0.536,0.854]"
> > "i:(0.854,1.32]"     "j:(1.32,3.81]"
> > >
> >
> > Thanks
> > Leo.
> >
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