[R] grid.arrange, grid.layout - legend, global y axis title

[Johannes Radinger]

Hello,

I created several plot with ggplot2 dev mode.

Now I want to combine the plots in a grid
e.g. 2x2 with a fixed size of the output.

What I am doing at the moment is:

grid.newpage() 
pushViewport(viewport(layout = grid.layout(nrow=2, ncol=2,
			widths = unit(c(7.5,6.5), "cm"),
		heights = unit(rep(5, 2), "cm"))))
print(plot1, vp = viewport(layout.pos.row = 1, layout.pos.col = 1))
print(plot2, vp = viewport(layout.pos.row = 1, layout.pos.col = 2))
print(plot3, vp = viewport(layout.pos.row = 2, layout.pos.col = 1))
print(plot4, vp = viewport(layout.pos.row = 2, layout.pos.col = 2))


This is working well so far.

The y-axis are for all plots the same so I'd like to have a global y-axis title on the left side. How can that be done using my approach?

I also would like to add a global vertical legend for my plots below all plots.
The legend should show the to different symbols (same as for the single plots (ggplot2)). I also don't know how to do that.

I know that there is the function grid.arrange which can do both things but this isn't working because I am in the dev mode of ggplot. Then I get the error: Error: could not find function "ggplotGrob.

I load my libraries the following way:

1) import data
2) load library(gridExtra)
3) load library(devtools)
   dev_mode(TRUE)
   library(ggplot2)
   library(reshape2)
4) produce plots
5) arrange the plots.

So what is the best way to proceed? 
Should I stay with the grid.layout approach and can I get there a global legend and a global y axis title?
Or how can I use grid.arrange, define the position of the gobal legend and set the single plot to a fixed size?

I hope that wasn't to complicated...

/Johannes
 
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