Place title of multiplot panel with ggplot2

Question

From the help found here I\'ve managed to create this multiplot panel: with the follow

Answer 1

If I understand correctly what you want to do, probably you can use +opts(title = XXX):

p1 <- ggplot(mtcars, aes(factor(cyl))) + geom_bar()
p2 <- ggplot(mtcars, aes(wt, mpg)) + geom_point()
p3 <- p2 + geom_line()

pushViewport(viewport(layout = grid.layout(2, 2)))  
print(p1 + opts(title = "bar"), 
  vp = viewport(layout.pos.row = 1, layout.pos.col = 1))     
print(p2 + opts(title = "point"), 
  vp = viewport(layout.pos.row = 1, layout.pos.col = 2))     
print(p3 + opts(title = "point and line"), 
  vp = viewport(layout.pos.row = 2, layout.pos.col = 1:2))

UPDATED

here is an example:

pushViewport(viewport(layout = grid.layout(3, 2, heights = unit(c(1, 4, 4), "null"))))
grid.text("title of this panel", vp = viewport(layout.pos.row = 1, layout.pos.col = 1:2))
print(p1, vp = viewport(layout.pos.row = 2, layout.pos.col = 1))
print(p2, vp = viewport(layout.pos.row = 2, layout.pos.col = 2))
print(p3, vp = viewport(layout.pos.row = 3, layout.pos.col = 1:2))

what you need to do is:

1. Make one extra row in grid.layout
2. Adjust width
3. Draw textGrob on the extra viewport row.

Answer 2

library(gridExtra)

p <- ggplot()

grid.arrange(p,p,p,p,p, top = "Title",
            layout_matrix = matrix(c(1,2,3,4,5,5), ncol=2, byrow=TRUE))