Add "title" to my factors using facet_grid

Question

I would like to add text / title for my factors using ggplot2.

For example, for data from the library {reshape2}:

library(reshape2) library(ggplot2) ggplot(tips, aes(x=total_bill, y=tip/total_bill)) + geom_point(shape=1) + facet_grid(sex ~ .) 

Stickers factors: Female and Male.

How can I add a “sex” heading over them?

Answer 1

Adapting this answer .

A little better. Design your own width.

 library(reshape2) library(ggplot2) library(grid) library(gtable) p = ggplot(tips, aes(x=total_bill, y=tip/total_bill)) + geom_point(shape=1) + facet_grid(sex ~ .) # text, size, colour for added text text = "SEX" size = 30 col = "red" face = "bold" # Convert the plot to a grob gt <- ggplotGrob(p) # Get the positions of the right strips in the layout: t = top, l = left, ... strip <-c(subset(gt$layout, grepl("strip-r", gt$layout$name), select = t:r)) # Text grob text.grob = textGrob(text, rot = -90, gp = gpar(fontsize = size, col = col, fontface = face)) # New column to the right of current strip # Adjusts its width to text size width = unit(2, "grobwidth", text.grob) + unit(1, "lines") gt <- gtable_add_cols(gt, width, max(strip$r)) # Add text grob to new column gt <- gtable_add_grob(gt, text.grob, t = min(strip$t), l = max(strip$r) + 1, b = max(strip$b)) # Draw it grid.newpage() grid.draw(gt) 

Original

 library(reshape2) library(ggplot2) library(grid) library(gtable) p = ggplot(tips, aes(x=total_bill, y=tip/total_bill)) + geom_point(shape=1) + facet_grid(sex ~ .) # Convert the plot to a grob gt <- ggplotGrob(p) # Get the positions of the right strips in the layout: t = top, l = left, ... strip <-c(subset(gt$layout, grepl("strip-r", gt$layout$name), select = t:r)) # New column to the right of current strip # Adjust the width to suit gt <- gtable_add_cols(gt, unit(3, "lines"), max(strip$r)) # Add text grob to new column; adjust cex (ie, size) to suit gt <- gtable_add_grob(gt, textGrob("SEX", rot = -90, gp = gpar(cex = 2, fontface = "bold", col = "RED")), t = min(strip$t), l = max(strip$r) + 1, b = max(strip$b)) # Draw it grid.newpage() grid.draw(gt)