[R] Order of factor levels

Guelman, Leo leo.guelman at rbc.com
Mon Jan 11 20:24:29 CET 2016

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.

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=":")


res <- main_fun(df)
 [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]"


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