I am plotting a collaborator network, where point size is scaled by the number of articles written in a country and lines between points represent collaborations, with line width and opacity scaled by number of collaborations. E.g.

library(tidyverse)

# data for lines
df_links <- structure(list(from = c("Argentina", "Argentina", "Canada",
                        "Austria", "Austria", "Italy", "Austria",
                        "Italy", "New Zealand"),
               to = c("Canada", "Germany", "Germany", "Italy",
                      "New Zealand", "New Zealand", "Panama",
                      "Panama", "Panama"), 
               collabs = c(1L, 1L, 2L, 1L, 1L, 1L, 1L, 1L, 1L),
               x = c(-64, -64, -106, 15, 15, 13, 15, 13, 175),
               y = c(-38, -38, 56, 48, 48, 42, 48, 42, -41),
               x_end = c(-106, 10, 10, 13, 175, 175, -81, -81, -81),
               y_end = c(56, 51, 51, 42,-41, -41, 9, 9, 9)),
          row.names = c(NA, -9L),
          class = c("tbl_df", "tbl", "data.frame"))

# data for points 
df_points <- structure(list(name = c("Argentina", "Austria", "Australia", 
                        "Canada", "Germany", "France", "United Kingdom", 
                        "Italy", "New Zealand", "Panama", "Venezuela"),
               papers = c(1L, 1L, 1L, 22L, 3L, 2L, 1L, 1L, 2L, 1L, 1L),
               x = c(-64, 15, 134, -106, 10, 2, -3, 13, 175, -81, -67),
               y = c(-38, 48, -25, 56, 51, 46, 55, 42, -41, 9, 6)),
          row.names = c(NA, -11L),
          class = c("tbl_df", "tbl", "data.frame"))

#plot
ggplot()   
  geom_curve(data = df_links,
             aes(x = x, y = y,
                 xend = x_end,
                 yend = y_end,
                 size = collabs,
                 alpha = collabs),
             curvature = 0.33)  
  geom_point(data = df_points,
             aes(x = x,
                 y = y,
                 size = papers),
             colour = "red")  
  coord_fixed(xlim = c(-150, 180), ylim = c(-55, 80))  
  theme_void()

My problem is with the legends. I want:

1. a legend named collabs which has line thickness and line opacity
2. a legend named papers which is point size

Instead I have papers and collabs (line size and point size) in one legend and opacity in a second. I think the issue is because I am using size inside aes for both geom_curve and geom_point?

E.g. I want something like this (edited in inkscape)

Any advice would be much appreciated!

CodePudding user response：

This could be achieved via the ggnewscale package which allows for multiple scales and legends for the same aesthetic:

library(tidyverse)
library(ggforce)
library(ggnewscale)

ggplot()   
  geom_curve(data = df_links,
             aes(x = x, y = y,
                 xend = x_end,
                 yend = y_end,
                 size = collabs,
                 alpha = collabs),
             curvature = 0.33)  
  new_scale("size")  
  geom_point(data = df_points,
             aes(x = x,
                 y = y,
                 size = papers),
             colour = "red")  
  coord_fixed(xlim = c(-150, 180), ylim = c(-55, 80))  
  theme_void()