在 R 中重命名 data.table 中的一些列

Question

i have a large data.table with many columns with numeric values which are long (ex 64891237094518350) It is hard to read, therefore, i would like to change the format of some columns. i tried :

datatable(my_data) %>% format(c("columnA", "columnB", "columnC"),
decimal.mark = ",", big.mark = " ", small.mark = ".", small.interval = 3)

however, nothing happens. I also tried:

my_data %>% format(c("columnA", "columnB", "columnC"),
decimal.mark = ",", big.mark = " ", small.mark = ".", small.interval = 3)

how can i fix this?

Answer 1

If we want only to do this on a subset of columns, use mutate_at

library(dplyr)
my_data %>%
    mutate_at(vars(country, state, DOB),
     ~ format(., decimal.mark = ",", big.mark = " ", 
          small.mark = ".", small.interval = 3))

The same logic in data.table would be

library(data.table)
nm1 <- c("country", "state", "DOB")
setDT(my_data)[, (nm1) := lapply(.SD, format, decimal.mark = ",", 
  big.mark = " ", small.mark = ".", small.interval = 3), .SDcols = nm1]