R/multiplot.R

In Rmisc: Ryan Miscellaneous

#' Multiple plot function
#' 
#' Renders multiple ggplot plots in one image
#' 
#' @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
#' 
#' @note 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.
#' 
#' @references http://www.cookbook-r.com/Graphs/Multiple_graphs_on_one_page_(ggplot2)
#' 
#' @importFrom grid grid.newpage grid.layout viewport pushViewport
#' 
#' @export
#' 
multiplot <- function(..., plotlist=NULL, cols=1, layout=NULL) {
  plots <- c(list(...), plotlist)
  numPlots = length(plots)
  if (is.null(layout))
    layout <- matrix(seq(1, cols * ceiling(numPlots/cols)),
                     ncol = cols, nrow = ceiling(numPlots/cols))
  if (numPlots==1) {
    print(plots[[1]])
  } else {
    grid.newpage()
    pushViewport(viewport(layout = grid.layout(nrow(layout), ncol(layout))))
    for (i in 1:numPlots) {
      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))
    }
  }
}