如何在R中为简单网络图添加标签？提供的代码

# 安装和加载igraph包
install.packages("igraph")
library(igraph)

# 创建一个简单的网络图
vertices <- c("Node 1", "Node 2", "Node 3", "Node 4")
edges <- c("Node 1", "Node 2", "Node 2", "Node 3", "Node 3", "Node 4", "Node 4", "Node 1")
graph <- graph(edges, vertices)

# 绘制网络图并添加标签
plot(graph, layout=layout_nicely)  # 绘制网络图

# 添加标签
labels <- c("Label 1", "Label 2", "Label 3", "Label 4")
text(x=coords(graph)[,1], y=coords(graph)[,2], labels=labels, col="red")