R igraph：无法设置边缘序列的属性

Question

我正在尝试根据某些标准使用 edge_attr（或者，set_edge_attr）来操作 R 中 igraph object 中边缘子集的属性。 例如，在下面的代码中，我试图将权重 = 1 的边的年龄属性加倍。

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)

但是，这会引发错误：

Error in `[[<-`(`*tmp*`, index, value = value) : 
attempt to select more than one element in vectorIndex

当我设置没有边缘序列的属性时，不会发生错误。 任何帮助将非常感激！

Answer 1

select 边缘的正确方法是：

edgeseq = E(graph)[weight==1]

注意区别：

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