Specify which legend to keep in wrap_plots

I'm looking to combine multiple graphs generated from different functions into a single display. Specifically, I want to only keep the legend of the first graph in the wrap.

Here is a minimal version of the problem:

library(ggplot2)
library(patchwork)

plot_histogram <- function() {
    plot_data <- ggplot(mtcars, aes(x = mpg, fill = factor(am))) +
        geom_histogram(binwidth = 2, color = "black") +
        labs(title = "Histo",
             x = "Miles/gallon",
             y = "nb cars",
             fill = "Transmission") +
        scale_fill_manual(values = c("skyblue", "salmon"), 
                          labels = c("Auto", "Man")) +
        theme_minimal() +
        theme(legend.position = "bottom")
    
    return(plot_data)
}

plot_scatter <- function() {
    plot_data <- ggplot(mtcars, aes(x = mpg, y = wt, color = factor(cyl))) +
        geom_point(size = 3) +
        labs(title = "Scatterplot",
             x = "Miles/gallon",
             y = "weight",
             color = "Cyl") +
        theme_minimal() +
        theme(legend.position = "bottom")
    
    return(plot_data)
}

scatter_plot_left <- plot_scatter()
scatter_plot_right <- plot_scatter()
histogram_plot <- plot_histogram()

combined_plots <- wrap_plots(scatter_plot_left + scatter_plot_right,
                             histogram_plot,
                             nrow = 1,
                             widths = c(3, 1)) +
    plot_layout(guides = 'collect') &
    theme(legend.position = "bottom")

combined_plots

Is there a way to preserve only the legend of the scatter plot?

From now, the best "solution" I've found is to wrap the first two graphs with guides = 'collect', and the wrap it with the other graph without keeping the legend.

This isn't really a solution, since the legend isn't centered and you have to adjust the size of the graphics each time, which isn't good in an automatic production process.

Solution

We can use layout design, which can work for both odd and even number of plots:

scatter_plot_left <- plot_scatter()
scatter_plot_middle <- plot_scatter()
scatter_plot_right <- plot_scatter()
histogram_plot <- plot_histogram() + theme(legend.position = "none") 

custom_lyt <- "AAABBBCCCDD
               AAABBBCCCDD
               AAABBBCCCDD
               AAABBBCCCDD
               AAABBBCCCDD
               AAABBBCCCDD
               AAABBBCCCDD
               AAABBBCCCDD
               ####ZZZ####"

scatter_plot_left + scatter_plot_middle + scatter_plot_right + 
    histogram_plot + 
    guide_area() +
  plot_layout(guides = 'collect', design = custom_lyt)

custom_lyt <- "AAACCCDD
               AAACCCDD
               AAACCCDD
               AAACCCDD
               AAACCCDD
               AAACCCDD
               AAACCCDD
               AAACCCDD
               ###ZZ###"

scatter_plot_left + scatter_plot_right + 
    histogram_plot + 
    guide_area() +
  plot_layout(guides = 'collect', design = custom_lyt)

^{Created on 2024-05-03 with reprex v2.0.2}