geom_nodes() requires more colors than there are nodes

[mkarikom]

Cross-posted at StackOverflow.

Create an igraph object with five vertices and two edges:

test <- structure(list(5, TRUE, c(0, 3), c(4, 1), c(0, 1), c(1, 0), c(0, 1, 1, 1, 2, 2), c(0, 0, 1, 1, 1, 2), list(c(1, 0, 1), structure(list(), .Names = character(0)),list(name = c("3", "6", "7", "2", "1")), list(weight = c(3.30310760667904, 3.55724789915966))), environment), class = "igraph")

Check the number of nodes and edges:

igraph::ecount(test)
#> [1] 2
igraph::vcount(test)
#> [1] 5

The following code works (it should not work, notice that the number of color values in geom_nodes() is wrong, there should be five values, but 7 are given):

ggplot(test, aes(x = x, y = y, xend = xend, yend = yend)) + 
  geom_edges(arrow = arrow(), color = 'black') + 
  geom_nodes(size =10, aes(color=1:7/(7))) + 
  scale_color_gradient(low = "green", high = "red")

See plot here.

If the correct number of values for geom_nodes(aes(color=<five values>)) is used instead, an error is generated:

ggplot(test, aes(x = x, y = y, xend = xend, yend = yend)) + 
  geom_edges(arrow = arrow(), color ='black') + 
  geom_nodes(size =10, aes(color=1:5/(5))) + 
  scale_color_gradient(low = "green", high = "red")
#> Error: Aesthetics must be either length 1 or the same as the data (7): colour

Notice that geom_nodes seems to require that color = nodes + edges, why is this?

Is there a way around this?

If there are 7 colors passed, how does it decide which 5 to use for the node colors?

[vinhbiochem]

Hi @briatte,

I'm having the same problem with geom_edges. I currently have 64 nodes and 108 edges, and when I try to use aes to color edges in a specific fashion, I'm asked to have a data length of 172. Please let me know what I should do.