R/grf_bar.R

In daltoolbox: Leveraging Experiment Lines to Data Analytics

#' @title Plot Bar Graph
#' @description Draw a simple bar chart from a two-column data frame: first
#'   column as categories (`x`), second as values (`y`).
#' @details If `colors` is provided, a constant fill is used; otherwise
#'   ggplot2's default palette applies. `alpha` controls bar transparency. The
#'   first column is coerced to factor when needed, which makes the function
#'   convenient for quick summaries of grouped values.
#' @param data Two-column data frame: category in the first column, numeric
#'   values in the second.
#' @param label_x Label for the x-axis.
#' @param label_y Label for the y-axis.
#' @param colors Optional fill color.
#' @param alpha Bar transparency between 0 and 1.
#' @return A `ggplot2::ggplot` object.
#' @references
#' Wickham, H. (2016). ggplot2: Elegant Graphics for Data Analysis. Springer.
#' @examples
#' # summarizing iris dataset
#' data <- iris |>
#'   dplyr::group_by(Species) |>
#'   dplyr::summarize(Sepal.Length = mean(Sepal.Length))
#' head(data)
#'
#' # plotting data
#' grf <- plot_bar(data, colors = "blue")
#' plot(grf)
#' @importFrom ggplot2 ggplot
#' @importFrom ggplot2 aes_string
#' @importFrom ggplot2 geom_bar
#' @importFrom ggplot2 theme_bw
#' @importFrom ggplot2 theme
#' @importFrom ggplot2 xlab
#' @importFrom ggplot2 ylab
#' @importFrom ggplot2 element_blank
#' @export
plot_bar <- function(data, label_x = "", label_y = "", colors = NULL, alpha = 1) {
  series <- as.data.frame(data)
  # ensure first column is categorical for discrete bars
  if (!is.factor(series[,1]))
    series[,1] <- as.factor(series[,1])
  x <- y <- NULL
  colnames(series)[1:2] <- c("x", "y")
  grf <- ggplot2::ggplot(series, ggplot2::aes(x = x, y = y))
  if (!is.null(colors)) {
    # fixed fill color
    grf <- grf + ggplot2::geom_bar(stat = "identity", fill = colors, alpha = alpha)
  }
  else {
    # default theme colors
    grf <- grf + ggplot2::geom_bar(stat = "identity", alpha = alpha)
  }
  grf <- grf + ggplot2::theme_bw(base_size = 10)
  grf <- grf + ggplot2::theme(panel.grid.minor = ggplot2::element_blank())
  grf <- grf + ggplot2::theme(legend.title = ggplot2::element_blank()) +
    ggplot2::theme(legend.position = "bottom")
  grf <- grf + ggplot2::xlab(label_x)
  grf <- grf + ggplot2::ylab(label_y)
  return(grf)
}