R igraph setting attribute incorrectly

Question

I’m trying to set_vertex_attribute to a graph and noticing that the function assigns attributes incorrectly. Similar issues have been reported here: R - Vertex attributes - 'Inappropriate value given in set.vertex.attribute.' But I’ve tried changing the class to character without luck. What could be the issue?

Data:

crops <- structure(list(target = c("Angola", "Angola", "Bahrain",
                                  "Benin", "Benin", "Bolivia"), source = c("Argentina",
                                                                                           "Botswana", "Bahrain", "Angola", "Bolivia", "Benin"), weight = c(112858157.048368,
                                                                                                                                                               45859551593.4988, 70972664.5057742, 1291072130433.34, 70268376116.3827,
                                                                                                                                                               410763090.329797)), row.names = c(NA, -6L), class = c("data.table",
                                                                                                                                                                                                                     "data.frame"))

com <- structure(list(name = c("Angola", "Argentina", "Bahrain", "Benin",
                               "Bolivia", "Botswana"), com = c(1L, 2L, 3L, 4L, 5L, 6L)), row.names = c(NA,
                                                                                                       6L), class = "data.frame")

Code:

g <- graph.data.frame(crops, directed=TRUE)

nodes <- get.data.frame(g, what = "vertices")

nodes_com <- merge(nodes,com, by = "name")

nodes_com$com <-  as.character(nodes_com$com)

g <- set_vertex_attr(g, "com", value = nodes_com$com) 

#validation test - here I discover V(g)$com is different than in nodes_com
df <- data.frame(name = V(g)$name, com = V(g)$com) 

Answer 1

I think you should use sort = FALSE when merge, e.g.,

nodes_com <- merge(nodes, com, by = "name", sort = FALSE)

and then you will obtain

> df
       name com
1    Angola   1
2   Bahrain   3
3     Benin   4
4   Bolivia   5
5 Argentina   2
6  Botswana   6

which has the same rows as in com

> com
       name com
1    Angola   1
2 Argentina   2
3   Bahrain   3
4     Benin   4
5   Bolivia   5
6  Botswana   6