I'm trying to manipulate the attributes of a subset of edges in an igraph object in R using edge_attr (or alternatively, set_edge_attr) based on certain criteria. For example, in the code below, I'm trying to double the age attribute of edges with weight = 1.
nodes <- data.frame(name=c('1', '4', '5', '6', '8'))
edges <- data.frame(
from = c('1', '4', '5', '1', '8', '1'),
to = c('4', '5', '6', '8', '6', '6'),
weight = c(1, 1, 1.5, 1.5, 2.5, 5),
age=c(48, 33, 45, 34, 21, 56)
)
graph = graph_from_data_frame(d = edges, vertices = nodes, directed=FALSE)
edgeseq = E(graph)[[weight==1]]
newage <- edge_attr(graph, "age", index = edgeseq)*2
edge_attr(graph, "age", edgeseq) <- newage
#Alternatively:
set_edge_attr(graph, "age", edgeseq, newage)
However, this throws an error:
Error in `[[<-`(`*tmp*`, index, value = value) :
attempt to select more than one element in vectorIndex
The error does not occur when I set the attributes without an edge sequence. Any help would be much appreciated!
The proper way to select edges is:
edgeseq = E(graph)[weight==1]
Note the difference:
E(graph)[weight==1]
+ 2/6 edges from 33d7121 (vertex names):
[1] 1--4 4--5
E(graph)[[weight==1]]
+ 2/6 edges from 33d7121 (vertex names):
tail head tid hid weight age
1 1 4 1 2 1 96
2 4 5 2 3 1 66