Remove page numbers from marrangeGrob (or arrangeList) pdf

Question

marrangeGrob in the gridExtra arranges grobs (usually ggplots in my case) in rows, columns and pages. It also numbers the pages.

require(ggplot2)
require(plyr)
require(gridExtra)

p <- function(plotdata) {
    x <- ggplot(plotdata, aes(wt, mpg)) + 
        geom_point() + 
        ggtitle(plotdata$gear[1])
    return(x)
}

all <- dlply(mtcars, .(gear), p)

allarranged <- do.call(marrangeGrob, c(all, nrow=1, ncol=2))
ggsave("multipage.pdf", allarranged, width=12)

That's a silly but reproducible example.

Now inspect the output of str(allarranged[[1]]) to reveal the objects of the page numbers. Reduced to the essentials, they're here:

[[1]]
  $ children     :List of 5
  ..$GRID.frame.1925:List of 6
  .. ..$ children     :List of 5
  .. .. ..$ GRID.cellGrob.1927:List of 10
  .. .. .. ..$ children     :List of 1
  .. .. .. .. ..$ GRID.text.1845:List of 11
  .. .. .. .. .. ..$ label        : chr "page 1 of 2"

I made up the first few lines there because I'm having trouble writing the output of str() to file. The point stands, though. $label is the problem-child of many grandparents. There are also several $labels per arrangelist (arrangeList is the output class of arrangeGrob).

Once you've figured out where the $labels are, then this works: allarranged[[1]]$children$GRID.frame.1770$children$GRID.cellGrob.1772$children$GRID.text.1690$label <- NULL

But how to predict that whole tree, or recurse through it looking for $labels? If that weren't such an interesting problem I'd probably just contact the gridExtra maintainer.

Answer 1

You need to pass top=NULL to marrangeGrob.

all <- dlply(mtcars, .(gear), p)

allarranged <- do.call(marrangeGrob, c(all, nrow=1, ncol=2, list(top=NULL) ))
ggsave("multipage.pdf", allarranged, width=12)