Dynamic Scale Injection for Edge Clipping

Utility function for RGraphSpace that enables edge layers to scan adjacent nodes and determine their dimensions. This information is used to compute arrow clipping offsets, preventing edge geometry from overlapping node symbols.

Usage

inject_nodespace(...)

Arguments

...

Additional parameters passed to other methods (currently ignored).

Value

An object of class inject_nodespace, which interacts with the ggplot2 + operator.

Details

This function operates in two stages within the ggplot2 workflow:

1. Capture: It scans the plot layers for a GeomNodeSpace to extract both mapping variables (from aes()) and static parameters (specifically size and stroke).

2. Injection: It locates GeomEdgeSpace layers and injects scale rules, captured mappings, and fixed parameters into the geometry parameters.

This "lazy injection" calculates edge clipping based on the actual scales used by the nodes, even if scales are defined after the layers.

Note: inject_nodespace() must be called last in the ggplot chain to allow the function to correctly scan all previously added layers and scales.

See also

geom_edgespace, geom_nodespace

Examples

library(igraph)
library(ggplot2)

# Generate a toy star graph
gtoy1 <- make_star(15, mode="out")

# Set node and edge attributes
V(gtoy1)$my_node_var <- runif(vcount(gtoy1), 1, 20)
E(gtoy1)$my_edge_var <-  runif(ecount(gtoy1), 1, 20)

# Create a GraphSpace object with a circular layout
gs <- GraphSpace(gtoy1, layout = layout_in_circle(gtoy1))
#> Validating the 'igraph' object...
#> Vertex attribute 'name' missing; assigning names... 
#> Creating a 'GraphSpace' object...

if (FALSE) { # \dontrun{
# Build the plot
# Note that inject_nodespace() is called at the end to
# synchronize node sizes with edge clipping.
ggplot() +
  geom_edgespace(aes(colour = my_edge_var), data = gs) +
  geom_nodespace(aes(size = my_node_var), data = gs) +
  scale_size(range = c(2, 15)) +
  inject_nodespace()
} # }