How can I arrange an arbitrary number of ggplots using grid.arrange?

Question

This is cross-posted on the ggplot2 google group

My situation is that I\'m working on a function that outputs an arbitrary number of plots

Answer 1

I'm answering a bit late, but stumbled on a solution at the R Graphics Cookbook that does something very similar using a custom function called multiplot. Perhaps it will help others who find this question. I'm also adding the answer as the solution may be newer than the other answers to this question.

Multiple graphs on one page (ggplot2)

Here's the current function, though please use the above link, as the author noted that it's been updated for ggplot2 0.9.3, which indicates it may change again.

# Multiple plot function
#
# 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.
#
multiplot <- function(..., plotlist=NULL, file, cols=1, layout=NULL) {
  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))
    }
  }
}

One creates plot objects:

p1 <- ggplot(...)
p2 <- ggplot(...)
# etc.

And then passes them to multiplot:

multiplot(p1, p2, ..., cols = n)