igraph错误无法创建顶点数为负的空图 [英] igraph error cannot create empty graph with negative number of vertices

问题描述

为什么在尝试创建下面的简单图形时会出现错误?如果我用数字替换"a"和"b"，那么它有效吗?任何解决方案

Why do I get an error when I try to create below simple graph? If i replace "a" and "b" with numbers then it works? any solution

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

推荐答案

在?graph中，您可以阅读:

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.

由于它正在寻找数字矢量，但是您已经给它输入了文本，因此它将所有字母转换为NA(这是强制引入的NA".

Since it's looking for a numeric vector but you've given it text, it's converting all the letters to NA (this is the "NAs introduced by coercion."

您可以将文本转换为适当的数字标识符，例如:

You could convert the text to appropriate numeric identifiers with something like:

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

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