How to align and scale plots of different dimensions with ggplot2, gridExtra?

Question

I'm trying to produce side by side tile plots using ggplot2 and gridExtra. However, the plots produced are not scaled/aligned, see the picture and code below.

How can I produce this figure such that the cells are aligned and of the same dimensions?

Code

library(ggplot2)
library(gridExtra)

## make date frames
one <- floor(runif(56, min=0, max=5))
data.one<- cbind(one,expand.grid(h = seq(1,8,1), w = seq(1,7,1)))

two <- floor(runif(35, min=0, max=5))
data.two <- cbind(two,expand.grid(h = seq(1,7,1), w = seq(1,5,1)))

## gridExtra layout
lay <- rbind(c(1,1,1,1,1,1,1,NA,NA,NA,NA,NA),
             c(1,1,1,1,1,1,1,2,2,2,2,2),
             c(1,1,1,1,1,1,1,2,2,2,2,2),
             c(1,1,1,1,1,1,1,2,2,2,2,2),
             c(1,1,1,1,1,1,1,2,2,2,2,2),
             c(1,1,1,1,1,1,1,2,2,2,2,2),
             c(1,1,1,1,1,1,1,2,2,2,2,2),
             c(1,1,1,1,1,1,1,2,2,2,2,2))

##plots
plot.one<-ggplot(data=data.one)+
  geom_tile(aes(x=w,y=h,fill=one),colour = "grey50")+ 
  scale_fill_gradient(low = "white", high = "blue")+
  theme(legend.position= "none")

plot.two<-ggplot(data=data.two)+
  geom_tile(aes(y=h,x=w,fill=two),colour = "grey50")+ 
  scale_fill_gradient(low = "white", high = "red")+
  theme(legend.position= "none")

grid.arrange(plot.one,plot.two, layout_matrix = lay)

Take a look at cowplot—it's got some solutions to simplify this type of situation, and is well-documented — camille

user10045075 user10045075 · Accepted Answer · 2018-07-07T03:47:46

ggplot2 doesn't assign fixed sizes to the plot panels, so you need to go to a rather low-level, find out the number of bins in each plot, and use this to set the appropriate panel size in the gtable object. The other complication is that "null" units are a bit special in grid, so to have something that scales with them it needs to be a null unit itself, as in this dummy rectGrob squeezing the second plot panel from the top,

b1 <- ggplot_build(p1)
b2 <- ggplot_build(p2)

n <- function(b) length(unique(b[["data"]][[1]][["y"]]))

library(egg)
library(grid)

gf1 <- gtable_frame(ggplot_gtable(b1))
gf2 <- gtable_frame(ggplot_gtable(b2))

gf2$grobs[[5]][["grobs"]][[1]] <- arrangeGrob(
  rectGrob(gp=gpar(fill="grey95", col=NA)),  gf2$grobs[[5]][["grobs"]][[1]],
  heights = unit.c(unit(1 - n(b2) / n(b1), "null"), unit(n(b2) / n(b1),"null")))

grid.arrange(gf1, gf2, ncol=2)

How to align and scale plots of different dimensions with ggplot2, gridExtra?

1 Answers