[R] Order of factor levels

[Guelman, Leo]

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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