Left align two graph edges (ggplot)

Question

I'm using ggplot and have two graphs that I want to display on top of each other. I used grid.arrange from gridExtra to stack them. The problem is I want the left edges of the graphs to align as well as the right edges regardless of axis labels. (the problem arises because the labels of one graph are short while the other is long).

The Question:
How can I do this? I am not married to grid.arrange but the ggplot2 is a must.

What I've tried:
I tried playing with widths and heights as well as ncol and nrow to make a 2 x 2 grid and place the visuals in opposite corners and then play with the widths but I couldn't get the visuals in opposite corners.

require(ggplot2);require(gridExtra)
A <- ggplot(CO2, aes(x=Plant)) + geom_bar() +coord_flip() 
B <- ggplot(CO2, aes(x=Type)) + geom_bar() +coord_flip() 
grid.arrange(A, B, ncol=1)

Answer 1

Using cowplot package:

A <- ggplot(CO2, aes(x=Plant)) + geom_bar() +coord_flip() 
B <- ggplot(CO2, aes(x=Type)) + geom_bar() +coord_flip() 

library(cowplot)
plot_grid(A, B, ncol=1, align="v")

Answer 2

Here is another possible solution using melt from the reshape2 package, and facet_wrap:

library(ggplot2)
library(reshape2)

dat = CO2[, c(1, 2)]
dat$id = seq(nrow(dat))
mdat = melt(dat, id.vars="id")

head(mdat)
#   id variable value
# 1  1    Plant   Qn1
# 2  2    Plant   Qn1
# 3  3    Plant   Qn1
# 4  4    Plant   Qn1
# 5  5    Plant   Qn1
# 6  6    Plant   Qn1

plot_1 = ggplot(mdat, aes(x=value)) + 
         geom_bar() + 
         coord_flip() +
         facet_wrap(~ variable, nrow=2, scales="free", drop=TRUE)

ggsave(plot=plot_1, filename="plot_1.png", height=4, width=6)