Evenly Spaced Month Charts

I recently noticed that ggplot2 spaces date axes literally even when grouped by month. I’ve been using ggplot2 extensively for years and I don’t remember noticing before, so this is not really a big deal, but now that I know it bugs me a lot. Take a look below.

As always, let’s load the tidyverse.

library(tidyverse)

Next, we need some example data. Nothing fancy, just something to plot as an example.

month_data <- tibble(dates = seq(ymd("2023-11-01"), ymd("2024-04-30"), by = "day"),                     data = sample(1:1e3, 182)) |>  mutate(month = floor_date(dates, "month")) |>  group_by(month) |>  summarise(monthly_mean = mean(data))month_data## # A tibble: 6 × 2##   month      monthly_mean##   <date>            <dbl>## 1 2023-11-01         572.## 2 2023-12-01         601.## 3 2024-01-01         471.## 4 2024-02-01         562.## 5 2024-03-01         487.## 6 2024-04-01         438.

Now let me show you how the distance between the months is not equal.

month_data |>  ggplot(aes(x = month, y = monthly_mean)) +  geom_col(width = 29) +  ggtitle("The Months Are Not Spaced Evenly!") +  # add the year to the first month plotted in each year  scale_x_date(labels = scales::label_date_short())

How frustrating! The fix is not that hard, though. We are going to change the date axis to factors with a neat little trick. We’re going to hack the label_date_short() function to change the dates to text and then change the dates to factors. Here we go.

# get the label_date_short() functionprettify_dates <- scales::label_date_short()# we use the new function we made and make the dates factors so that they sort # correctly. new_month_data <- month_data |>  mutate(pretty_month = prettify_dates(month),         pretty_month = as_factor(pretty_month))new_month_data## # A tibble: 6 × 3##   month      monthly_mean pretty_month##   <date>            <dbl> <fct>       ## 1 2023-11-01         572. "Nov\n2023" ## 2 2023-12-01         601. "Dec"       ## 3 2024-01-01         471. "Jan\n2024" ## 4 2024-02-01         562. "Feb"       ## 5 2024-03-01         487. "Mar"       ## 6 2024-04-01         438. "Apr"

Now all we have to do is drop the date scale and let geom_col() chose its own width.

new_month_data |>  ggplot(aes(x = pretty_month, y = monthly_mean)) +  geom_col() +  ggtitle("The Spacing Is Even Now!")