## c:/Dropbox/Rpackages/CLmisc/R/keep_cols_by_ref.R
## Chandler Lutz
## Questions/comments: cl.eco@cbs.dk
## $Revisions: 1.0.0 $Date: 2018-10-23
#' Select columns in a data.table by reference
#'
#' @param DT a \code{data.table}
#' @param keep.cols a character vector of columns in \code{DT}
#' @examples
#' data(mtcars)
#' DT <- as.data.table(mtcars)
#' DT <- select_by_ref(DT, "hp")
#' head(DT)
#'
#' @export
select_by_ref <- function(DT, keep.cols) {
if (!is.data.table(DT)) stop("Error: `DT` needs to be a data.table")
if (!is.character(keep.cols)) stop("Error: `keep.cols` must be a character vector")
delete.cols <- names(DT) %>% .[!(. %chin% keep.cols)]
DT <- DT[, c(delete.cols) := NULL]
return(DT)
}
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