igraph错误无法创建具有负数顶点的空图

Question

当我尝试创建下面的简单图表时，为什么会出现错误？如果我用数字替换“a”和“b”，那么它可以工作吗？任何解决方案

g1 <- graph(c("a","b"),directed=TRUE)

错误是

Error in graph(c("a", "b"), directed = TRUE) : 
  At type_indexededgelist.c:117 : cannot create empty graph with negative number of vertices, Invalid value
In addition: Warning messages:
1: In graph(c("a", "b"), directed = TRUE) : NAs introduced by coercion
2: In graph(c("a", "b"), directed = TRUE) : NAs introduced by coercion

Answer 1

从?graph，您可以读到：

edges: Numeric vector defining the edges, the first edge points from the first element to the second, the second edge from the third to the fourth, etc.

由于它正在寻找一个数字向量，但你给了它文本，它会将所有字母转换为NA（这是“强制引入的 NA”。）

您可以使用以下内容将文本转换为适当的数字标识符：

g1 <- graph(as.numeric(factor(c("a","b"))), directed=TRUE)