graph-operators-by-name

Graph operators based on symbolic vertex names

Normally igraph operators are based on internal igraph vertex ids. This function works with vertex names instead.

Usage

graph.intersection.by.name(g1, g2, keep.x.vertices = FALSE,
      keep.x.vertex.attributes = FALSE,
      keep.x.edge.attributes = FALSE)
graph.union.by.name(g1, g2)
graph.difference.by.name(g1, g2, keep.x.vertex.attributes = FALSE,
      keep.x.edge.attributes = FALSE)

Details

These functions treat the graphs as sets of ordered (if they are directed), or unordered (if they are undirected) pairs of symbolic vertex names and perform set operations on them.

concept

Graph operators

See Also

graph.union, link{graph.intersection} and link{graph.difference} for the functions that are based on vertex ids.

Aliases

• graph.intersection.by.name
• graph.union.by.name
• graph.difference.by.name

Examples

# Print attributes as well
igraph.options(print.vertex.attributes=TRUE,
               print.edge.attributes=TRUE)

# Creating a wheel graph
g1 <- graph.ring(10)
V(g1)$name <- letters[1:vcount(g1)]
g2 <- graph.star(11, mode="undirected")
V(g2)$name <- c("z", letters[1:vcount(g1)])
g <- graph.union.by.name(g1, g2)
if (interactive()) {
  plot(g, layout=layout.kamada.kawai, vertex.label=V(g)$name)
}
g

# Some more examples
g1 <- graph.formula(a-b-c)
V(g1)$v.attr=c(1,2,3)
E(g1)$e.attr=c(5,7)
g2 <- graph.formula(b-c-d)

# Test the functions
graph.intersection.by.name(g1,g2) # Vertices are intersected as well
graph.union.by.name(g1,g2)        # Vertices are unioned as well
graph.difference.by.name(g1,g2)   # Vertices from x (g1) are used

# graph.intersection.by.name() has some extra parameters
graph.intersection.by.name(g1,g2,
    keep.x.vertices          = TRUE) # Keep all x vertices (only intersect edges)

graph.intersection.by.name(g1,g2,
    keep.x.vertices          = FALSE, # Keep all x vertices (only intersect edges)
    keep.x.vertex.attributes = TRUE, # Don't throw away V(g1) attributes
    keep.x.edge.attributes   = TRUE) # Don't throw away E(g1) attributes

# graph.difference.by.name() has some extra parameters
graph.difference.by.name(g1,g2,
    keep.x.vertex.attributes = TRUE, # Don't throw away V(g1) attributes
    keep.x.edge.attributes   = TRUE) # Don't throw away E(g1) attributes