R data.table keys and column names. Harmonisation - r

Question

I am trying to set keys yo a data.table and keep the original column names on the second row. All that I have tried so far changes the column names to keys and erases the original variables. I have ten data.tables to merge and all the variables have different names like in the example. So I made keys but would like to keep the originals as well before harmonisation just to be sure.
library(tidyverse)
library(lubridate)
library(forcats)
library(stringr)
library(data.table)
library(rio)
library(dplyr)
1. Keys
keys1 <- c("SDC_GENDER","SDC_CHILD_NB","LAB_CRP","PM_HIP")
keys2 <- c("SDC_GENDER","SDC_CHILD_NB","LAB_CRP","PM_HIP")
2. data.table example with variable names.
TD3 = data.table(q128 = c(1, 2, 1, 2), q129 = c(1, 5, 2, 4), q130 = c(0.8, 3.0, 10.0, NA), q131 = c(55, 56, 80, 79))
TD3
TD4 = data.table(q128 = c(1, 1, 1, 2), q129 = c(1, 3, 2, 999), q130 = c(0.9, 3.1, NA, 9.0), q131 = c(58, 60, 45, NA))
TD4

Answer 1

I'm not sure this is really the data structure you want to have, that is to have mixed variable types like r2evans said. However...this solution works. Just put all your little data.tables into a list and voila.
I noticed that keys1 and keys2 are identical, so I just used one of them. If they should be different keys for each they can also be listed.
keys1 <- c("SDC_GENDER","SDC_CHILD_NB","LAB_CRP","PM_HIP")
TD <- list()
TD[[1]] = data.table(q128 = c(1, 2, 1, 2), q129 = c(1, 5, 2, 4), q130 = c(0.8, 3.0, 10.0, NA), q131 = c(55, 56, 80, 79))
TD[[2]] = data.table(q128 = c(1, 1, 1, 2), q129 = c(1, 3, 2, 999), q130 = c(0.9, 3.1, NA, 9.0), q131 = c(58, 60, 45, NA))
TD <- lapply(TD, FUN = function(x){
oldcolumns <- colnames(x)
td <- data.table(
'V1' = oldcolumns[1],
'V2' = oldcolumns[2],
'V3' = oldcolumns[3],
'V4' = oldcolumns[4]
)
colnames(td) <- keys1
colnames(x) <- keys1
x <- rbind(td, x)
return(x)
})