## S3 method for class 'igraph':
+(e1, e2)
union
.disjoint_union
.vertex
orvertices
function, then new vertices are added to the
graph. This form is appropriate when one wants to add some vertex
attributes as well. The operands of thevertices
function
specifies the number of vertices to add and their attributes as
well. The unnamed arguments ofvertices
are concatenated and
used as thename
vertex
is just an alias tovertices
, and it is
provided for readability. The user should use it if a single vertex
is added to the graph.
edge
oredges
function, then new edges will be added to the
graph. The new edges and possibly their attributes can be specified as
the arguments of theedges
function. The unnamed arguments ofedges
are concatenated and used
as vertex ids of the end points of the new edges. The named
arguments will be added as edge attributes.
Examples:g <- make_empty_graph() +
vertices(letters[1:10]) +
vertices("foo", "bar", "bar2", "foobar2")
g <- g + edge("a", "b")
g <- g + edges("foo", "bar", "bar2", "foobar2")
g <- g + edges(c("bar", "foo", "foobar2", "bar2"), color="red", weight=1:2)See more examples below.edge
is just an alias toedges
and it is provided
for readability. The user should use it if a single edge is added to
the graph.
path
function, then
new edges that form a path are added. The edges and possibly their
attributes are specified as the arguments to thepath
function. The non-named arguments are concatenated and interpreted
as the vertex ids along the path. The remaining arguments are added
as edge attributes.Examples:g <- make_empty_graph() + vertices(letters[1:10]) g <- g + path("a", "b", "c", "d") g <- g + path("e", "f", "g", weight=1:2, color="red") g <- g + path(c("f", "c", "j", "d"), width=1:3, color="green")
It is important to note that, although the plus operator is commutative, i.e. is possible to write graph <- "foo" + make_empty_graph() it is not associative, e.g. graph <- "foo" + "bar" + make_empty_graph() results a syntax error, unless parentheses are used: graph <- "foo" + ( "bar" + make_empty_graph() ) For clarity, we suggest to always put the graph object on the left hand side of the operator: graph <- make_empty_graph() + "foo" + "bar"
-.igraph
,
igraph-minus
; add.edges
,
add_edges
; add.vertices
,
add_vertices
; delete.edges
,
delete_edges
;
delete.vertices
,
delete_vertices
; edge
,
edges
; path
;
vertex
, vertices
# 10 vertices named a,b,c,... and no edges
g <- make_empty_graph() + vertices(letters[1:10])
# Add edges to make it a ring
g <- g + path(letters[1:10], letters[1], color = "grey")
# Add some extra random edges
g <- g + edges(sample(V(g), 10, replace = TRUE), color = "red")
g$layout <- layout_in_circle
plot(g)
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