ggplot objects can be passed in. If the layout is something like matrix(c(1,2,3,3), nrow=2, byrow=TRUE), then plot 1 will go in the upper left, 2 will go in the upper right, and 3 will go all the way across the bottom.
multiplot(..., plotlist = NULL, file, cols = 1, layout = NULL)
list of `ggplot` objects
A matrix specifying the layout. If present, 'cols' is ignored.
Number of columns in layout
multiplot(g, g2, g3) Make a list from the ... arguments and plotlist If layout is NULL, then use 'cols' to determine layout Make the panel ncol: Number of columns of plots nrow: Number of rows needed, calculated from #' of cols Set up the page Make each plot, in the correct location Get the i,j matrix positions of the regions that contain this subplot