R multiplot

gridExtra.R

library(gridExtra)

a <- qplot(TMPRSS4, ECADHERIN, data=spear)
b <- qplot(TMPRSS4, ECADHERIN, data=spear, geom="jitter")

grid.arrange(a,b,ncol=2)

viewport.R

library(ggplot2)
library(grid)

#generate a new page, or erase the current one.
grid.newpage()

#maintain a Viewport tree, which describe the regions and coordinate systems.
pushViewport(viewport(layout=grid.layout(1,2)))

#generate two ggplot2 objects.
a <- qplot(TMPRSS4, ECADHERIN, data=spear)
b <- qplot(TMPRSS4, ECADHERIN, data=spear, geom="jitter")

#print them into the Viewport, or the page.
print(a, vp=viewport(layout.pos.row=1,layout.pos.col=1))
print(b, vp=viewport(layout.pos.row=1,layout.pos.col=2))

#also, you can define a function to make the print process more concise.

You can refer to http://www.anaharb.com/2014/0228/R-grid-n-into-1/