R/select_rows.R

In syberia/syberiaMungebits2: syberiaMungebits2 (http://github.com/syberia/syberiaMungebits2)

#' @include mungebit_template.R
NULL

#' Select rows in a dataframe.
#'
#' @name select_rows
#' @param dataframe a data.frame
#' @param rows an atomic vector or function. Drop all but these rows.
#'    If \code{rows} is a function, the rows will be selected based on the
#'    \code{whole} parameter. If \code{whole = TRUE}, the whole dataframe
#'    will be passed in, and the resulting row indices (character, numeric,
#'    or logical) will be selected. If \code{whole = FALSE} (the default)
#'    the function will be applied to each row and the result will be expected
#'    to be a logical, with only the rows returning \code{TRUE} being selected.
#' @param whole a logical. See the \code{rows} parameter. The default is 
#'    \code{FALSE}.
#' @param ... additional arguments to \code{rows} is that parameter is a function. 
#' @export
#' @examples \dontrun{
#' select_rows()$run(iris, 1:10) # Select only first ten rows
#' select_rows()$run(iris, c(TRUE,FALSE)) # Select only odd rows
#' iris2 <- iris; rownames(iris2) <- paste0("row", 1:nrow(iris2))
#' select_rows()$run(iris, c("row10", "row51")) # Select rows by name
#' }
select_rows <- mungebit_template({
  train <- predict <- function(dataframe, rows, whole = FALSE, ...) {
    if (is.function(rows)) {
      if (isTRUE(whole)) {
        rows <- rows(dataframe)
      } else {
        rows <- apply(dataframe, 1, rows, ...)
      }
    }
    dataframe <- dataframe[rows, ]
  }
})