How to align an ordinary ggplot with a faceted one in cowplot?

Question

I\'m trying to arrange plots for publication with the use of cowplot package.
I just want the panels to be equally sized and labelled.

Reproducibl

Answer 1

Update: egg package is on CRAN now
https://cran.r-project.org/web/packages/egg/index.html

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I just want to add that @baptiste has created a great experimental package egg, which accomplishes what he wrote in his answer:

Install it from github (https://github.com/baptiste/egg)

library("devtools")
install_github("baptiste/egg")

Then simply do

library("egg")
ggarrange(gg1, gg2, ncol=2)

You can add labels manually:

ap <- ggarrange(gg1,gg2, ncol=2)
ggdraw(ap) + draw_plot_label(label=c("a","b"), x=c(0,0.5), y=c(1,1))

(When I tried to first add the labels to the individual plots, the plots didn't get arranged properly.)