Iterative link of tables in R

Question

I am studying a topic of networks and need to represent all the connections between a Vertice and those connected to it, directly and indirectly, so I thought to make an iterative link between tables of the type:

Be the table to be used in left_join:

ligacoes <- data.frame(origem=c("A","A", "B", "B", "D"), 
                       destino=c("B","D","C","D", "E"), 
                       valor=c(31.2, 100, 1, 85, 2))

I intended to represent all links with origin at vertex A, so I thought to perform a left Join between the table links and the table links connecting the destination column of the first with the source column of the second, as many times as the match returns results (in this sample example only 2 left Join since the 3rd left_join no longer returns results however in the dataset there may be cases where a higher left_join number is required). Can someone help me? Obg

Answer 1

A simpler way to do what you need is to represent your data as graph. The igraph package is great for this. Expand your example to include links that do not start from A:

library(igraph)

ligacoes <- data.frame(
  origem  = c("A", "A", "B", "B", "D", "F", "G", "F"),
  destino = c("B", "D", "C", "D", "E", "G", "H", "H"),
  valor = c(31.2, 100, 1, 85, 2, 4, 7, 8))

# Converte os dados de origem e destino em objeto igraph
grafo <- graph.edgelist(as.matrix(ligacoes[1:2]))

# Inclui a variável valor como atributo das conexões:
E(grafo)$valor <- ligacoes$valor

plot(grafo)

The functions *ego are used to identify the vicinity of a node. A make_ego_graph returns the neighborhoods as a list of igraph objects (as there may be more than one), preserving the attributes. Using the option order (maximum number of connections up to the given nodes) with a rather high value, will have all connections with A. The option mode = "out" indicates to follow outgoing connections.

grafoA <- make_ego_graph(grafo, order = 1e9, nodes = "A", mode = "out")[[1]]

plot(grafoA, edge.label = E(grafoA)$valor)

plot(grafoA)