R/multiplot.R

In DrPaulWilliamson/ENVS450: Helper functions for ENVS450

multiplot <- function(..., plotlist=NULL, cols=1, layout=NULL) {
    
  # Multiple plot function
  #
  # Function to plot multiple ggplots side-by-side in same graphics window
  #
  # Adapted from http://www.cookbook-r.com/Graphs/Multiple_graphs_on_one_page_(ggplot2)/
  #
  # ggplot objects can be passed in ..., or to plotlist (as a list of ggplot objects)
  # - cols:   Number of columns in layout
  # - layout: A matrix specifying the layout. If present, 'cols' is ignored.
  #
  # 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.
  
  #require(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))
    }
  }
}