R/aveytoolkit_Multiplot.R

In stefanavey/aveytoolkit: Toolkit of Helper Functions

##' Multiplot
##'
##' Multiple Plot Function for ggplot
##'
##' @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
##' @details 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.
##' @author R Cookbook
##' @references \url{http://www.cookbook-r.com/Graphs/Multiple_graphs_on_one_page_\%28ggplot2\%29/}
##' @export
##' @examples
##' library(ggplot2)
##' 
##' ## This example uses the ChickWeight dataset, which comes with ggplot2
##' ## First plot
##' p1 <- ggplot(ChickWeight, aes(x=Time, y=weight, colour=Diet, group=Chick)) +
##'   geom_line() +
##'   ggtitle("Growth curve for individual chicks")
##' 
##'                                         # Second plot
##' p2 <- ggplot(ChickWeight, aes(x=Time, y=weight, colour=Diet)) +
##'   geom_point(alpha=.3) +
##'   geom_smooth(alpha=.2, size=1) +
##'   ggtitle("Fitted growth curve per diet")
##' 
##'                                         # Third plot
##' p3 <- ggplot(subset(ChickWeight, Time==21), aes(x=weight, colour=Diet)) +
##'   geom_density() +
##'   ggtitle("Final weight, by diet")
##' 
##'                                         # Fourth plot
##' p4 <- ggplot(subset(ChickWeight, Time==21), aes(x=weight, fill=Diet)) +
##'   geom_histogram(colour="black", binwidth=50) +
##'   facet_grid(Diet ~ .) +
##'   ggtitle("Final weight, by diet") +
##'   theme(legend.position="none")        # No legend (redundant in this graph)
##' 
##' Multiplot(p1, p2, p3, p4, cols=2)
Multiplot <- function(..., plotlist=NULL, file, 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::grid.newpage()
      grid::pushViewport(grid::viewport(layout = grid::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 = grid::viewport(layout.pos.row = matchidx$row,
                              layout.pos.col = matchidx$col))
      }
    }
}