ggplot2 extension advent of code: set_theme_last_plot()

[EvaMaeRey]

Thinking about this workflow, I thought his might be a good 'advent of code' challenge: https://bsky.app/profile/gforb.bsky.social/post/3lciojslcuc2t

'Copy and pasting the same + theme(...) line into every plot.'

I'd though about a variant: 1) build plot (explore data) 1.b) make plot look good; adjust plot w/ theme() 2) set theme based on last plot w/ set_theme_last_plot() 3) keep plotting.

I didn't manage to write a working set_theme_last_plot()! I think I need to make t1 look like t2 before trying to write the set_theme_last_plot() function.

library(ggplot2)
ggplot(data = cars) +
  aes(x = speed, y = dist) + 
  geom_point() + 
  theme(panel.grid = ggplot2::element_blank())

t1 <- last_plot()$theme  # add class theme and gg

t2 <- ggplot2::theme(
        panel.grid = ggplot2::element_blank(),
        complete = TRUE 
      ) 

waldo::compare(t1, t2)
#> `old` is a list
#> `new` is an S3 object of class <theme/gg>, a list

^{Created on 2024-12-09 with reprex v2.1.0}

[yjunechoe]

Fun experiment! I don't have anything to contribute because I rarely use theme(), but can I suggest some names? :D

• persist_theme()
• recycle_theme()
• repeat_theme()

Or perhaps less side-effect-y:

plot1 + theme_linedraw()

plot2 + theme_last_plot()

[EvaMaeRey]

Nice ideas!

[teunbrand]

Just here to point that the obvious solution doesn't work.
The reason is that ggplot() uses set_last_plot() internally, so when you're requesting the theme of the previous plot, while building the next plot, it is going to point to itself. I.e. in the example below, last_theme() retrieves the theme in ggplot(mtcars, ...).

library(ggplot2)

last_theme <- function(plot = last_plot()) plot$theme

ggplot(mpg, aes(displ, hwy)) +
  geom_point() +
  theme(text = element_text(colour = "red"))

ggplot(mtcars, aes(disp, mpg)) +
  geom_point() +
  last_theme() +
  theme(line = element_line(linetype = "dotted"))

^{Created on 2024-12-09 with reprex v2.1.1}

[teunbrand]

The 3rd case is any time you add anything with + via ggplot2:::add_ggplot()

[EvaMaeRey]

I was more interested in a set_theme_update_to_last() even if side affect-y. I'm think my problem (classing the list as gg and theme) is a different one than is demonstrated?

library(ggplot2)
theme_set(theme_dark())
ggplot(cars) +
  aes(x = speed, y = dist) + 
  geom_point() + 
  theme(panel.grid = element_blank())

theme_update_last_plot <- function(){
  
  theme_get() %+replace% 
      theme(
      panel.grid = element_blank(),  # would like to use last_plot()$theme somehow here
      complete = TRUE   
      ) 
  
}

theme_set(theme_update_last_plot())

ggplot(mtcars) + 
  aes(wt, mpg) + 
  geom_point()

^{Created on 2024-12-09 with reprex v2.1.0}

[teunbrand]

Something like the following?

theme_update_last_plot <- function(plot = last_plot()){
  theme_get() + plot$theme
}

[EvaMaeRey]

That seems to work, yes! I didn't expect theme_get() + last_plot()$theme to work as an input for theme_set()! I kind of like it because it's exploratory in theme construction (inspect as you go) and then you and reuse your work w/o copy-paste. I might not fully appreciate the side affects concerns.

library(ggplot2)

theme_set_last_plot <- function(){
  
  theme_set(theme_get() + last_plot()$theme)
  
}

ggplot(cars) +
  aes(x = speed, y = dist) + 
  geom_point() +
  theme(panel.grid = element_blank())

theme_set_last_plot()

ggplot(mtcars) + 
  aes(wt, mpg) + 
  geom_point()

^{Created on 2024-12-09 with reprex v2.1.0}

[EvaMaeRey]

New application w/ focus on paper, ink, accent focus! So easy to create ad-hoc chalkboard theme - w/ chalk_themed geoms! 🤯

library(ggplot2)

# theme_set_last_plot <- function(){
#   
#   theme_set(theme_get() + last_plot()$theme)
#   
# }

ggplot(cars) +
  aes(x = speed, y = dist) + 
  geom_point() +
  theme_classic(ink = alpha("lightyellow", .7),
                paper = "darkseagreen4",
                base_size = 18) + 
  geom_smooth() + 
  theme(geom = element_geom(accent = "orange")) + 
  theme(plot.title.position = "plot") +
  labs(title = "My ad-hoc chalkboard theme,\nwith new ink, paper, accent arguments!") ->
p; p
#> `geom_smooth()` using method = 'loess' and formula = 'y ~ x'

  
(theme_get() + last_plot()$theme) |> theme_set()

ggplot(mtcars) + 
  aes(wt, mpg) + 
  geom_point() + 
  geom_smooth() + 
  labs(title = "Themed consistent w/ previous plot where\ninteractive theming work was done!")
#> `geom_smooth()` using method = 'loess' and formula = 'y ~ x'

^{Created on 2024-12-17 with reprex v2.1.0}