R functions – convenient extensions of data.table's `setnames` function

data.table_setnames_extensions.R

library(magrittr)
library(data.table)

setnamesWithArrows <- function(dt, ...) {
  pairs <-  
    substitute(list(...)) %>% 
    as.list %>% 
    tail(-1) %>% 
    lapply(. %>% as.list %>% tail(-1) %>% rev) 
  from <-
    pairs %>% 
    sapply(. %>% .[[1]] %>% as.character)
  to <-
    pairs %>% 
    sapply(. %>% .[[2]] %>% as.character)
  setnames(dt, from, to)
}

setnamesWithFunction <- function(dt, FUN)
  setnames(dt,
           colnames(dt),
           colnames(dt) %>% sapply(FUN))

# ### Usage examples
#   
# > x <- data.table(a = 1, b = 2)
# 
# > x %>% setnamesWithArrows(a -> Aa, b -> bB) %>% print()
# 
#         Aa    bB
#      <num> <num>
#   1:     1     2
# 
# > x %>% setnamesWithFunction(toupper) %>% print()
# 
#         AA    BB
#      <num> <num>
#   1:     1     2