Function for label variable before plotting in R - r

Question

I hope, this question is not too easy for this forum (actually, I'm almost a bit embarrassed to ask this question here, but I'm struggeling with this small issue the whole day...)
I have dataframes look like the following:
df <- data.frame(runif(4),
c("po", "pr", "po", "pr"),
c("Control 1","Control 1", "Treatment 1", "Treatment 1"))
names(df) <- list("values", "test_type", "group")
Now, I want easliy re-label the variables "test_type" and "group" for the plot afterwards. (it's nicer to read "pretest" instead of "pr" in a presentation :-) )
I could do it manually with:
df$test_type <- factor(df$test_type,
levels = c("pr", "po"),
labels = c("pretest", "posttest"))
df$group <- factor(df$group,
levels = c("Control 1", "Treatment 1"),
labels = c("control", "EST"))
In this case, I would have to repeat this for a lot more dataframes, which lead me to write a function:
var_label <- function(df, test, groups){
# Create labels
df$test_type <- factor(df$test,
levels = c("pr", "po"),
labels = c("pretest", "posttest"))
df$group <- factor(df$groups,
levels = c("Control 1", "Treatment 1"),
labels = c("control", "EST"))
return(list(df$test_type, df$group))
}
Unfortunately, this doesn't work. I tried a lot slight different versions and also different command from the Hmisc package, but none of these worked. I know, I can solve this problem in another way, but I try to write more efficient and shorter codes and would be really interested, what I have to change to make this function work. Or even better do you have a suggestion for a more efficient way?
Thank you a lot in advance!!

Answer 1

As I mentioned above, I think forcats::fct_relabel() is what you want here, along with dplyr::mutate_at(). Assuming that your relabeling needs are no more complex than what has been outlined in your question, the following should get you what you appear to be looking for.
####BEGIN YOUR DATAFRAME CREATION####
df <- data.frame(runif(4),
c("po", "pr", "po", "pr"),
c("Control 1","Control 1", "Treatment 1", "Treatment 1"))
names(df) <- list("values", "test_type", "group")
#####END YOUR DATAFRAME CREATION#####
# Load dplyr and forcats
library(dplyr)
library(forcats)
# create a map of labels and levels based on your implied logic
# the setup is label = level
label_map <- c("pretest" = "pr"
,"posttest" = "po"
,"control" = "Control 1"
,"EST" = "Treatment 1")
# create a function to exploit the label map
fct_label_select <- function(x, map) {
names(which(map == x))
}
# create a function which is responsive to a character vector
# as required by fct_relabel
fct_relabeler <- function(x, map) {
unlist(lapply(x, fct_label_select, map = map))
}
fct_relabeler(levels(df$test_type), map = label_map)
# function to meet your apparent needs
var_label <- function(df, cols, map){
df %>%
mutate_at(.vars = cols
,.fun = fct_relabeler
,map = map)
}
var_label(df = df, cols = c("test_type", "group"), map = label_map)
# values test_type group
# 1 0.05159681 posttest control
# 2 0.89050323 pretest control
# 3 0.42988881 posttest EST
# 4 0.32012811 pretest EST