R/multiplot.R

In MaximilianBernkopf/maxxxy: Usefull packages for my workflows

#' Create multi-panel plots
#'
#' ggplot objects can be passed in ..., or to plotlist (as a list of ggplot objects)
#'
#' @param ... ggplot objects
#' @param plotlist A list of ggplot objects
#' @param cols Number of columns in layout
#' @param layout A matrix specifying the layout. If present, 'cols' is ignored.
#'
#' @return a multi-panel plot
#'
#' If the layout is something like matrix(c(1,2,3,3), nrow=2, byrow=TRUE),
#' then plot 1 will go in the upper left, 2 will go in the upper right, and
#' 3 will go all the way across the bottom.
#'
#' @import grid
#' @import tidyverse
#'
#' @export
#'
#' @examples
#' library(tidyverse)
#' library(maxxxy)
#'
#' p1 <- iris %>%
#'   as_tibble() %>%
#'   ggplot(aes(Sepal.Width, Sepal.Length, color = Species)) +
#'   geom_point()
#'
#' p2 <- iris %>%
#'   as_tibble() %>%
#'   ggplot(aes(Sepal.Width, fill = Species)) +
#'   geom_density(alpha = 0.5)
#'
#' p3 <- iris %>%
#'   as_tibble() %>%
#'   ggplot(aes(Species, Sepal.Width, fill = Species)) +
#'   geom_boxplot()
#'
#' multiplot(p1, p2, p3)
#'
multiplot <- function(..., plotlist = NULL, cols = 1, layout = NULL) {

  # Make a list from the ... arguments and plotlist
  plots <- c(list(...), plotlist)

  numPlots = length(plots)

  # If layout is NULL, then use 'cols' to determine layout
  if (is.null(layout)) {
    # Make the panel
    # ncol: Number of columns of plots
    # nrow: Number of rows needed, calculated from # of cols
    layout <- matrix(seq(1, cols * ceiling(numPlots/cols)),
                     ncol = cols, nrow = ceiling(numPlots/cols))
  }

  if (numPlots==1) {
    print(plots[[1]])

  } else {
    # Set up the page
    grid.newpage()
    pushViewport(viewport(layout = grid.layout(nrow(layout), ncol(layout))))

    # Make each plot, in the correct location
    for (i in 1:numPlots) {
      # Get the i,j matrix positions of the regions that contain this subplot
      matchidx <- as.data.frame(which(layout == i, arr.ind = TRUE))

      print(plots[[i]], vp = viewport(layout.pos.row = matchidx$row,
                                      layout.pos.col = matchidx$col))
    }
  }
}