geom_tile and facet_grid/facet_wrap for same height of tiles

Question

Using ggplot, I would like represent a graph tile with panel, but with same height tile for each panel. I have this graph : ``` dataSta <- list(sites=rep(paste("S", 1:31),each=12), month=rep(1:12,31), value=round(runif(31*12, min=0, max=3000)), panel=c(rep("Group 1",16*12),rep("Group 2", 12*12), rep("Group 3", 3*12))) library(ggplot2) library(grid) base_size <- 9 windows() ggplot(data.frame(dataSta), aes(factor(month), sites)) + geom_tile(aes(fill = value), colour = "black")+ facet_wrap(~panel, scale="free_y", nrow=3)+ theme_grey(base_size = base_size) + labs(x = "",y = "") + scale_x_discrete(expand = c(0, 0)) + scale_y_discrete(expand = c(0, 0)) + theme(legend.title = element_blank(), axis.ticks = element_blank(), axis.text.x = element_text(size = base_size *0.8, hjust = 0), panel.margin = unit(0,"lines"), strip.text = element_text(colour="red3", size=10, face=2)) ``` But height of tiles is different between panel. I try to use facet_grid : ``` windows() ggplot(data.frame(dataSta), a…

Accepted Answer

You can look at what ggplot contains before plotting, and rescale the panels accordingly.

```
g <- ggplot_build(p) 
## find out how many y-breaks are in each panel
## to infer the number of tiles
vtiles <- sapply(lapply(g$panel$ranges, "[[", "y.major"), length)

## convert the plot to a gtable object 
gt <- ggplot_gtable(g)
## find out which items in the layout correspond to the panels
## we refer to the "t" (top) index of the layout
panels <- gt$layout$t[grepl("panel", gt$layout$name)]
## replace the default panel heights (1null) with relative sizes 
## null units scale relative to each other, so we scale with the number of tiles
gt$heights[panels] <-lapply(vtiles, unit, "null")
## draw on a clean slate
library(grid)
grid.newpage()
grid.draw(gt)
```

geom_tile and facet_grid/facet_wrap for same height of tiles

Solution

Problem