Adjust size of legend ticks

September 26, 2023

I would like to make the coloured lines in the legend thicker, as they are too hard to distinguish now. I tried using override.aes inside the scale_color_manual function, or inside the guides function, but either does nothing, or increases the size of the legend, but not of the ticks themselves. I’ve also tried playing with different value sizes in scale_shape_manual but also to no avail. Here is a sample of my code below.

library(ggplot2)
library(dplyr)
library(countrycode)

set.seed(123)

temp <- data.frame(
  Year = rep(1995:2020, times = 12), 
  Country = rep(c("ABW", "AFG", "AGO", "AIA", "ALB", "AND", "ANT", "ARE", "ARG", "ARM", "AUT", "ETH"), each = 26), 
  deg_in_norm = runif(12 * 26, min = 0, max = 1), 
  deg_out_norm = runif(12 * 26, min = 0, max = 1) 
)

highlighted_countries <- c("ZAF", "SAU", "RUS", "IRN", "IND", "ETH", "EGY", "CHN", "BRA", "ARG", "ARE")
temp <- temp %>%
  mutate(Color = ifelse(Country %in% highlighted_countries, as.character(Country), "Not BRICS")) %>%
  mutate(Size = ifelse(Country %in% highlighted_countries, 1, 0)) %>%
  mutate(Full_names = ifelse(Country %in% highlighted_countries, 
                             countrycode(Country, origin = 'iso3c', destination = 'country.name'), 
                             "Not BRICS")) %>%
  group_by(Country) %>%
  mutate(id = cur_group_id()) %>%
  ungroup()

ggplot(data = temp) +
  geom_line(aes(x = Year, y = deg_in_norm, 
                color = factor(Color), size = factor(Size), group = id)) +
  scale_color_manual(values = c("ARE" = "black", "ARG" = "#6699CC", "ETH" = "#44AA99",
                                "Not BRICS" = "grey"),
                     labels = c("United Arab Emirates", "Argentina", "Ethiopia",
                                "Not BRICS")) +
  scale_size_manual(values = c("0" = 0.5, "1" = 1.5), guide = "none") + 
  guides(color = guide_legend(override.aes = list(size = 15) ) ) +  
  theme(legend.position = "bottom") +
  labs(y = "Normalised In-Degree\n")

This gives this picture:

>Solution :

You should listen to your warning messages:

Warning message:
Using `size` aesthetic for lines was deprecated in ggplot2 3.4.0.
ℹ Please use `linewidth` instead.
This warning is displayed once every 8 hours.
Call `lifecycle::last_lifecycle_warnings()` to see where this warning was
generated.

Changing size to linewidth does the trick:

ggplot(data = temp) +
  geom_line(aes(x = Year, y = deg_in_norm, 
                color = factor(Color), linewidth = factor(Size), group = id)) +
  scale_color_manual(values = c("ARE" = "black", "ARG" = "#6699CC", "ETH" = "#44AA99",
                                "Not BRICS" = "grey"),
                     labels = c("United Arab Emirates", "Argentina", "Ethiopia",
                                "Not BRICS")) +
  scale_linewidth_manual(values = c("0" = 0.5, "1" = 1.5), guide = "none") + 
  guides(color = guide_legend(override.aes = list(linewidth = 15) ) ) +  
  theme(legend.position = "bottom") +
  labs(y = "Normalised In-Degree\n")