juggleR: A mix of useful R functions

#' Plot count data with ggplot2
#'
#' Create a bar plot of count (frequency) data that is stored in a data.frame
#'   or table.
#'
#' The argument to this function is expected to be either a data.frame or a
#'  table.
#'
#' If a data.frame is provided, it must have exactly two columns:
#'   the first column contains the of unique values in the data, and the second
#'   column is the corresponding integer frequencies to each value.
#'
#' If a table is provided, it must have exactly one row: the rownames are the
#' unique values in the data, and the row values are the  corresponding integer
#' frequencies to each value.
#'
#' @param x A data.frame or table. See 'Details' for more information.
#' @param ... Extra parameters to pass to the barplot. Any parameter that
#' \code{geom_bar()} accepts can be used. For example, \code{fill = "red"} can
#' be used to make the bars red.
#'
#' @return A ggplot2 object that can have more layers added onto it.
#'
#' @examples
#' plotCount(table(infert$education))
#' df <- data.frame("vehicle" = c("bicycle", "car", "unicycle", "Boeing747"),
#'                  "NumWheels" = c(2, 4, 1, 16))
#' plotCount(df)
#'
#' @importFrom ggplot2 ggplot aes_string geom_bar
#'
#' @export

plotCount <- function(x, ...) {
  x <- data.frame(x)
  stopifnot(
    ncol(x) == 2,
    is.numeric(x[, 2]),
    all.equal(as.integer(x[, 2]), x[, 2]),
    length(x[, 1]) == length(unique(x[, 1]))
  )
  p <-
    ggplot2::ggplot(x) +
    ggplot2::aes_string(colnames(x)[1], colnames(x)[2]) +
    ggplot2::geom_bar(stat = "identity", ...)
  p
}