R ggraph/ggplot2 color legend not displayed properly

Question

I'm pretty new to ggraph and strugling a bit to get the legend to properly display the colors of the nodes. I have the following example data set:

nodes <- data.frame( ID =  c( 2, 3, 4, 5, 6, 7 ),  
                     cl = c( "A", "B", "A", "A", "C", "B" ), 
                     ty = c( 1, 1, 0, 0, 0, 1 ), 
                     assets = c( 20000000, 10000, 500000, 10000, 150, 50 )
                    )


edges <- data.frame( from = c( 2, 5, 4, 6, 7, 4, 3 ), 
                     to = c( 3, 4, 3, 5, 5, 3, 2 ), 
                     we = c( 1, 1, 3, 2, 1, 1, 3 ), 
                     pa = c( 0, 0, 1, 0, 1, 0, 0 ))

Based on these data I tried to plot the graph:

library( 'tidygraph' )
library( 'igraph' )
library( 'ggraph' )

graph <- graph_from_data_frame( edges, vertices = nodes, directed = TRUE ) %>% as_tbl_graph()


ggraph( graph, layout = 'fr' ) + 
  # Create edge layer
    geom_edge_link0( aes( width = we, color = factor( pa )), 
                          arrow = arrow( angle = 10, length = unit( 0.15, "inches" ),
                                         ends = "last", type = "closed" )) +
    scale_edge_width( range = c( 0.2, 2.2 )) +
    scale_edge_color_grey( start = 0.4, end = 0.8 ) +
  # Create node layer
    geom_node_point( aes( shape = factor( ty ), fill = cl, size = log( assets ))) +
  # Title and legend
    labs( edge_width = "Power", edge_color = "Ownertype" ) +
    ggtitle( "Title" ) +
    theme( legend.key = element_rect( fill = "white", colour = "black" ), 
    legend.title = element_text(face = "bold" )) +
    scale_size_continuous( name = "Assets", range = c( 3, 6 ), breaks = c( 5, 10, 15 )) +
    scale_shape_manual( name = "Same branch", values = c( 21, 23 ), labels = c( "no", "yes" )) +
    scale_fill_brewer( name = "Sector", palette = "Dark2" ) 

I have two issues with the legend under heading 'Sector':

1. The color keys are not displayed, they are all black. This happens everytime I let both the color and the shape of the nodes vary.
2. The color keys are too small, so that it is really hard to distinguish the colors (once they are there).

Unfortunately all my attempts to solve these two problems have been unsuccessful.

Answer 1

By default, the legend guide for points doesn't use a shape that supports a fill color. You need to set such a shape for the guide:

+ guides(fill = guide_legend(override.aes = list(size = 5, shape = 21)))