ox_union: Union of 'osm_graph' objects

In osmnxr: Download, Model and Analyze 'OpenStreetMap' Street Networks

Union of osm_graph objects

Description

Combines two or more graphs into a single osm_graph. Node and edge tables are stacked; nodes sharing an osmid are merged (the first occurrence wins) and edges duplicated across graphs are dropped. Attribute columns present in one graph but not another are filled with NA.

Usage

ox_union(..., dedupe_edges = TRUE)

Arguments

...	Two or more osm_graph objects, or a single list of them. All must share the same CRS.
dedupe_edges	Drop edges that appear in more than one graph with identical u, v and geometry (as happens when unioning overlapping downloads). Default TRUE.

Details

Nodes with the same osmid are treated as the same location, which is what stitches the graphs together: overlapping downloads share their OSM node ids, and a hand-built network (say, a metro layer) connects to a street graph wherever its edges reference street-node osmids. Custom networks should therefore use node ids that do not collide with OSM's except where a connection is intended (negative ids are a safe choice).

Value

An osm_graph. meta$network_type concatenates the distinct input types (e.g. "drive+walk"), meta$simplified is TRUE only if every input was simplified, and meta$union_of records how many graphs were combined.

Examples

g1 <- example_osm_graph(n = 3)

# a second, disjoint network with its own node ids
g2 <- example_osm_graph(n = 3)
g2$nodes$osmid <- g2$nodes$osmid + 1000
g2$edges$u <- g2$edges$u + 1000
g2$edges$v <- g2$edges$v + 1000

u <- ox_union(g1, g2)
u

# unioning overlapping graphs dedupes shared nodes and edges
nrow(ox_union(g1, g1)$edges) == nrow(g1$edges)

osmnxr documentation built on Oct. 20, 2026, 1:07 a.m.