makegraph: Construct graph

In cppRouting: Algorithms for Routing and Solving the Traffic Assignment Problem

Construct graph

Description

Construct graph

Usage

makegraph(
  df,
  directed = TRUE,
  coords = NULL,
  aux = NULL,
  capacity = NULL,
  alpha = NULL,
  beta = NULL
)

Arguments

df	A data.frame or matrix containing 3 columns: from, to, cost. See details.
directed	logical. If FALSE, then all edges are duplicated by inverting 'from' and 'to' nodes.
coords	Optional. A data.frame or matrix containing all nodes coordinates. Columns order should be 'node_ID', 'X', 'Y'.
aux	Optional. A vector or a single value describing an additional edge weight.
capacity	Optional. A vector or a single value describing edge capacity. Used for traffic assignment.
alpha	Optional. A vector or a single value describing alpha parameter. Used for traffic assignment.
beta	Optional. A vector or a single value describing beta parameter. Used for traffic assignment.

Details

'from' and 'to' are character or numeric vector containing nodes IDs. 'cost' is a non-negative numeric vector describing the cost (e.g time, distance) between each 'from' and 'to' nodes. coords should not be angles (e.g latitude and longitude), but expressed in a projection system. aux is an additional weight describing each edge. Shortest paths are always computed using 'cost' but aux can be summed over shortest paths. capacity, alpha and beta are parameters used in the Volume Delay Function (VDF) to equilibrate traffic in the network. See assign_traffic. capacity, alpha, beta and aux must have a length equal to nrow(df). If a single value is provided, this value is replicated for each edge. alpha must be different from 0 and alpha must be greater or equal to 1. For more details and examples about traffic assignment, please see the package website : https://github.com/vlarmet/cppRouting/blob/master/README.md

Value

Named list with two useful attributes for the user :

nbnode : total number of vertices
dict$ref : vertices IDs

Examples

#Data describing edges of the graph
edges<-data.frame(from_vertex=c(0,0,1,1,2,2,3,4,4),
                  to_vertex=c(1,3,2,4,4,5,1,3,5),
                  cost=c(9,2,11,3,5,12,4,1,6))

#Construct directed and undirected graph
directed_graph<-makegraph(edges,directed=TRUE)
non_directed<-makegraph(edges,directed=FALSE)

#Visualizing directed and undirected graphs
if(requireNamespace("igraph",quietly = TRUE)){
  plot(igraph::graph_from_data_frame(edges))
  plot(igraph::graph_from_data_frame(edges,directed=FALSE))
}

#Coordinates of each nodes
coord<-data.frame(node=c(0,1,2,3,4,5),X=c(2,2,2,0,0,0),Y=c(0,2,2,0,2,4))

#Construct graph with coordinates
directed_graph2<-makegraph(edges, directed=TRUE, coords=coord)

cppRouting documentation built on Dec. 1, 2022, 5:08 p.m.