Lowercase all character columns except xyz in dataframe-CodePudding

foo() is made to lowercase all character columns of a dataframe except= the ones whose names are provided by the user.

I wonder why when I provide except="study", foo incorrectly lowercases the column study in the data?

Reproducible code and desired output are below.

m="
study cap  back
AA    L    1
BB    F    2
CC    H    8"
data <- read.table(text=m,h=T)


foo <- function(X, except = NULL){
  y <- sapply(setdiff(names(X), except), function(x) is.character(as.vector(X[[x]])))
  X[y] <- lapply(X[y], tolower)
return(X)
}
#=== EXAMPLE OF USE:
foo(data, except = c("study"))

Desired_output=
"
study cap  back
AA    l    1
BB    f    2
CC    h    8"

CodePudding user response：

Here are two ways to achieve this -

Base R -

foo <- function(X, except = NULL){
  y <- names(Filter(is.character, X[setdiff(names(X), except)]))
  X[y] <- lapply(X[y], tolower)
  return(X)
}
foo(data, except = c("study"))

#  study cap back
#1    AA   l    1
#2    BB   f    2
#3    CC   h    8

Using dplyr -

library(dplyr)

foo <- function(X, except = NULL){
  X %>%
    mutate(across(where(is.character) & 
                  all_of(setdiff(names(X), except)), tolower))
}

foo(data, except = c("study"))

CodePudding user response：

data <- data.frame(
  Study = c("AA", "BB", "CC"),
  Cap = c("L", "F", "H"),
  Back = c(1, 2, 8))

foo <- function(X, except){
  targs <- setdiff(names(X), except)
  colnames(X)[which(names(X) %in% targs)] <- tolower(targs)
  return(X)
}

except <- "Study"

foo(data, except)
#>   Study cap back
#> 1    AA   L    1
#> 2    BB   F    2
#> 3    CC   H    8
Created on 2021-12-10 by the reprex package (v2.0.1)