Demonstrating laying out plots in a 'tree' structure using gridExtra

hierarchical_layout.R

library(ggplot2)
library(gridExtra)

## create 17 plots, where the only element is a number in the centre
res <- list()
for(i in 1:17) {
    x <- data.frame(x = 1, y = 1, num = as.character(i))
    res[[i]] <- ggplot(x, aes(x = x, y = y, label = num)) + 
        geom_text() +
        theme_void() +
        NULL
}

## create a heirarchical layout matrix
## there's probably a more elegant way of doing this
nrow <- ceiling(log2( length(res) + 1 ))
ncol <- 2^(nrow-1)
layout <- matrix(0, nrow = nrow, ncol = ncol)
for(i in 1:nrow) {
    j <- i-1
    vals <- (2^j):(2^(j+1)-1)
    layout[i,] <- rep( vals, each = ncol/length(vals) )
}

## plot using our layout matrix
grid.arrange(grobs=res[1:17] , layout_matrix = mat)