dist_calc {rSDI}

Distance Calculation for Graph Nodes

Description

This function calculates distances between each pair of nodes in the graph. It supports both Haversine and Euclidean formula. The function automatically selects the formula based on the availabe vertex attributes: 'x' and 'y' for Euclidean distances, 'latitude' and 'longitude' for Haversine distances.

Usage

dist_calc(g, formula = NULL)

Arguments

g

An igraph object, with nodes that have a combination of 'latitude' and 'longitude', or 'x' and 'y' vertices attributes.

formula

Optional parameter to specify the distance calculation formula to use, either 'Haversine' or 'Euclidean'. By default 'formula = NULL' and if not specified the otherwise, the function automatically determines the formula based on the available vertex attributes. [x, y] => Euclidean, [latitude,longitude] => Haversine. Note that the 'g' must have one of this set of vertex attributes.

Value

An igraph object with an additional edge attribute 'distance' that contains the calculated distances between each pair of nodes.

Examples

# Assuming 'g' is a graph object with latitude and longitude or x and y attributes for each node.
# an overall example
flows<-data.frame(from=c("A","B","A"), to=c("B","A","C"), weight=c(10,20,5))

# user provides x and y vertices
nodes<-data.frame(id=c("A","B","C","D"),x=c(0,4,0,4),y=c(3,0,0,3))

g<-igraph::graph_from_data_frame(flows, directed=TRUE, vertices=nodes)


dist_calc(g) # eucl. dist. calculated
dist_calc(g, formula = 'Euclidean') # calculates euc when asked
#dist_calc(g, formula = 'Haversine') # error

# user provides latitude and longitude vertices instead of x&y
nodes<-data.frame(id=c("A","B","C","D"),latitude=c(0,4,0,4),longitude=c(3,0,0,3))

g<-igraph::graph_from_data_frame(flows, directed=TRUE, vertices=nodes)

dist_calc(g) # haversine dist calculated
dist_calc(g, formula = 'Haversine') # calculated hav when asked specificallly
#dist_calc(g, formula = 'Euclidean') # error