R/multiplot.R

In hferg/btrtools:

#' Multiple plot function
#'
#' ggplot objects can be passed in ..., or to plotlist (as a list of ggplot objects)
#' HFG: From http://www.cookbook-r.com/Graphs/Multiple_graphs_on_one_page_%28ggplot2%29/.
#' 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.
#' @param cols   Number of columns in layout
#' @param layout A matrix specifying the layout. If present, 'cols' is ignored.
#' @param plotlist A list of plot objects (as opposed to individual objects)
#' @examples
#' multiplot(plot1, plot2, plot3, plot4, cols = 2)
#' all.plots <- list(plo1, plot2, plot3, plot4)
#' multiplot(plotlist = all.plots, cols = 2)

multiplot <- function(..., plotlist=NULL, file, cols=1, layout=NULL) {
  library(grid)

  # 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))
    }
  }
}