R/data-frame.R

In fuj: Functions and Utilities for Jordan

#' Quick DF
#'
#' This is a speedier implementation of `as.data.frame()` but does not provide
#' the same sort of checks. It should be used with caution.
#'
#' @return A `data.frame`; if `x` is `NULL` a `data.frame` with `0` rows and `0`
#'   columns is returned (similar to calling `data.frame()` but faster).
#'   `empty_df()` returns a `data.frame` with `0` rows and `0` columns.
#'
#' @examples
#' # unnamed will use make.names()
#' x <- list(1:10, letters[1:10])
#' quick_df(x)
#'
#' # named is preferred
#' names(x) <- c("numbers", "letters")
#' quick_df(x)
#'
#' # empty data.frame
#' empty_df() # or quick_df(NULL)
#'
#' @name quick_df
NULL

#' @export
#' @rdname quick_df
#' @param x A list or `NULL` (see return)
quick_df <- function(x = NULL) {
  if (is.null(x)) {
    return(.empty_df)
  }

  if (!is.list(x)) {
    stop(cond_quick_df_input())
  }

  n <- unique(lengths(x))

  switch(
    length(n) + 1L,
    .empty_df,
    struct(
      x = x,
      class = "data.frame",
      names = names(x) %||% seq_along(x),
      row.names = c(NA_integer_, -n)
    ),
    stop(cond_quick_df_list())
  )
}

#' @export
#' @rdname quick_df
empty_df <- function() {
  .empty_df
}

# pre-build a `data.frame` with the `struct()` utility from fuj.  Is this
# really necessary?  Only if we want the absolute best times for
.empty_df <- NULL
delayedAssign(
  ".empty_df",
  struct(list(), "data.frame", row.names = integer(), names = character())
)

#' @export
#' @rdname quick_df
#' @param ... Columns as `tag = value` (passed to `list()`)
quick_dfl <- function(...) {
  quick_df(lst(...))
}

#' Data frame
#'
#' Unsure if I want to export this
#'
#' @rdname quick_df
#' @noRd
dataframe <- quick_dfl


# conditions --------------------------------------------------------------

cond_quick_df_list <- function() {
  new_condition("`x` does not have equal length", class = "quick_df_list")
}

cond_quick_df_input <- function() {
  new_condition("`x` is not a list", class = "quick_df_input")
}