R/printing.R

In burchill/zplyr: Zach Burchill's Personal Functions

#' Print within pipes
#'
#' This function can be placed within a sequence of \code{\%>\%} pipes for debugging purposes.
#' It will literally print the output of the function you specify on whatever was passed into it, and then pass it out, untouched.  If you want to just print a string with no bearing on whatever is being piped, then set the `.text` variable to that string.
#'
#' @param .x Whatever is being piped down the pipeline
#' @param .f A function, formula, or atomic vector, which will be applied to `.x` and whose output will be printed. `print_and_pass()` uses the \code{\link[purrr]{as_mapper}} to turn this value into a function, so see that documentation. By default, it will just print `x`.
#' @param .text When explicitly set to a non-`NULL` value, `print_and_pass` with just print that value instead. It is intended to be a string, if used.
#' @param \dots Additional \emph{named} arguments for whatever function is being passed in.
#' @return The value of `.x`
#' @examples
#' df <- data.frame(x=runif(10))
#' new_df <- df %>%
#'   print_and_pass(.text="BEGIN DEBUG") %>%
#'   dplyr::mutate(y=x+4) %>%
#'   print_and_pass(~.$y) %>%
#'   dplyr::filter(y>4) %>%
#'   print_and_pass(.text="END DEBUG")
#' @export
print_and_pass <- function(.x, .f=identity, .text=NULL, ...) {
  if (!is.null(.text)) print(.text)
  else {
    .f <- purrr::as_mapper(.f, ...)
    print(.f(.x))
  }
  return(.x)
}


#' Print the head of a data frame/tibble
#'
#' This is just a convenience function that takes the head of a data frame and prints it using `print.data.frame()`, which will display all olumns, even if the data frame is a tibble.
#'
#' @param df A data frame, tibble, etc.
#' @param n Number of rows to grab with `head`
#' @param \dots Additional arguments for `print.data.frame`
#' @export
zead <- function(df, n = 6L, ...) {
  print.data.frame(head(df, n=n), ...)
}