gjabel - 4 months ago 25

R Question

I am combining facet plots of tiles. I want each tile to be square, or at least take the same height and width.

So far I have managed to give equal height to each row of tiles using

`layout_matrix`

Some code based on

`mtcars`

`library("tidyverse")`

library("gridExtra")

df0 <- mtcars %>%

group_by(cyl) %>%

count()

df1 <- mtcars %>%

rownames_to_column("car") %>%

mutate(man = gsub("([A-Za-z]+).*", "\\1", car))

g <- list()

for(i in 1:nrow(df0)){

g[[i]] <- ggplot(data = df1 %>% filter(cyl == df0$cyl[i]),

mapping = aes(x = "", y = car, fill = qsec)) +

geom_tile() +

facet_grid( man ~ ., scales = "free_y", space = "free") +

labs(x = "", y = "") +

guides(fill = FALSE) +

theme(strip.text.y = element_text(angle=0)) +

coord_fixed()

}

m0 <- cbind(c(rep(1, df0$n[1]), rep(NA, max(df0$n) - df0$n[1])),

c(rep(2, df0$n[2]), rep(NA, max(df0$n) - df0$n[2])),

c(rep(3, df0$n[3]), rep(NA, max(df0$n) - df0$n[3])))

grid.arrange(grobs = g, layout_matrix = m0)

Which produces this plot (minus my MS Paint skills):

Presumably the different lengths of the labels in the strip text and y axis lead to the different widths for the plotting area. Not sure how I can avoid this behavior though? I thought I could create on big

`facet_grid`

Answer

Turns out this is a rather tricky thing to do. Luckily, `cowplot::plot_grid`

can already do the alignment that results in equal sizes of the columns. I just took that function and removed the fluff, and decoupled the heights from the grid pattern it normally uses. We end up with a little custom function that does the job (all credits to Claus Wilke):

```
plot_grid_gjabel <- function(plots, heights) {
grobs <- lapply(plots, function(x) {
if (!is.null(x))
cowplot:::ggplot_to_gtable(x)
else NULL
})
num_plots <- length(plots)
num_widths <- unique(lapply(grobs, function(x) {
length(x$widths)
}))
num_widths[num_widths == 0] <- NULL
max_widths <- do.call(grid::unit.pmax,
lapply(grobs, function(x) { x$widths }))
for (i in 1:num_plots) {
grobs[[i]]$widths <- max_widths
}
width <- 1 / num_plots
height <- heights / max(heights)
x <- cumsum(width[rep(1, num_plots)]) - width
p <- cowplot::ggdraw()
for (i in seq_along(plots)) {
p <- p + cowplot::draw_grob(grid::grobTree(grobs[[i]]), x[i], 1 - height[i],
width, height[i])
}
return(p)
}
```

We can simply call this like so:

```
plot_grid_gjabel(g, df0$n)
```

Resulting in: