removing all the space between two ggplots combined with grid.arrange

Question

I want to stick two plots without any space between theme (so they share one axis).

Given:

p1 <- qplot(1,1,xlab="")

p1 <- p1 +
  theme(legend.position="none",
        axis.text.x=element_blank(),
        axis.ticks.x=element_blank(),
        plot.margin=unit(c(1,1,0,1), "cm"),
        panel.margin=unit(c(1,1,0,1), "cm"))
p2 <- qplot(1,2)

grid.arrange(p1,p2)

Which produces:

I want to eliminate the white space between the two plots.

I have the impression tweaking heights, as has been done for widths in : left align two graph edges (ggplot) is the solution, but can't figure it out.

Answer 1

You should provide plot.margin for both plots and set negative value for the bottom margin for p1 and upper margin for p2. This will ensure that both plot joins.

p1 <-  qplot(1,1,xlab="")+
  theme(legend.position="none",
        axis.text.x=element_blank(),
        axis.ticks.x=element_blank(),
        plot.margin=unit(c(1,1,-0.5,1), "cm"))
p2 <- qplot(1,2)+
  theme(legend.position="none",
        plot.margin=unit(c(-0.5,1,1,1), "cm"))


grid.arrange(p1,p2)

Answer 2

try

+ labs(x=NULL)

OR

+ labs(x=NULL, y=NULL)

to remove the left and bottom margins around the plots (p1, p2) before using grid.arrange

p1 <- qplot(1,1)+
 theme_bw() +
 theme(axis.text.x=element_blank(),
 axis.ticks.x=element_blank(),
 plot.margin = rep(unit(0,"null"),4),
 panel.margin = unit(0,"null"),
 axis.ticks.length = unit(0,"null"),
 axis.ticks.margin = unit(0,"null")) +
 labs(x=NULL)
p2 <- qplot(1,2)+
 theme_bw() +
 theme(
 plot.margin = rep(unit(0,"null"),4),
 panel.margin = unit(0,"null"),
 axis.ticks.length = unit(0,"null"),
 axis.ticks.margin = unit(0,"null"))

grid.arrange(p1,p2)