Easy way to split one field into n facets

[rjake]

I often create a heat map that is too long to display on one chart. I have to scratch my head each time to figure out how to break it into columns. I eventually end up with some integer division solution x %/% y like here:

Code

library(tidyverse)
library(scales)

df <- 
  USJudgeRatings |> 
  as_tibble(rownames = "y") |> 
  gather(x, fill, -y) |> 
  mutate(
    x = fct_reorder(x, fill, mean),
    y = fct_reorder(y, fill, sum, .desc = FALSE)
  ) |> 
  print()

# number of columns for plot
n_col <- 2

# separate into columns and keep factor order
plot_prep <- 
  df |> 
  mutate(
    y_order = as.integer(y),
    max_rows = ceiling(n_distinct(y) / n_col),
    facets = (-y_order %/% max_rows) # needs something to facet on, need '-' to keep highest values on left
  ) |> 
  print()

# plot
p <- 
  plot_prep |> 
  ggplot(aes(x, y, fill = fill)) +
  facet_wrap(~facets, ncol = n_col, scales = "free_y") +
  geom_tile(color = "white", size = 0.5) +
  scale_fill_stepsn(breaks = breaks_pretty(6), colours = viridis_pal()(5)) +
  theme(
    strip.background.y = element_blank(),
    strip.text = element_blank(),
    axis.text = element_text(size = 7)
  )

p + theme(aspect.ratio = 1)

# identify aspect ratio
aspect <- 
  plot_prep |> 
  select(x, y) |> 
  summarise_all(n_distinct) |> 
  mutate(ratio = y / x / n_col) |> 
  print() 

p + theme(aspect.ratio = aspect$ratio) # <------ fixed 1:1 size

Could a solution be implemented like one of these?

• facet_wrap(facets = ~., ncol = 2) -- currently just keeps chart as-is (no facets)
• a helper function facet_wrap(facets = split_facet(ncol = 2))
• a new function facet_split(ncol = 2)

---

Additionally, I often struggle to get the ratios correct.
coord_fixed() throws an error and aspect.ratio affects each panel rather than "unit of y per unit of x".
I included code ☝️ to show how I do it: [# unique y] / [# unique x] / [# of cols]

I originally posted in the ggplot2 repo tidyverse/ggplot2#4763 but was directed to work with other package creators who might be able to take this on. I ❤️ ggforce and think it could be a good home for this type of faceting.

[thomasp85]

I like the idea but I do unfortunately not have the bandwidth to develop such a thing at the moment. I'll leave it open in case someone else want to take it on and create a PR