r - 当我尝试使用库 github 中的 ggbiplot 时出错

Question

我正在尝试使用以下代码使用绘图功能 ggbiplot：

  install.packages("devtools")
  library(devtools)
  install_github("vqv/ggbiplot")

  g <- ggbiplot(iris.pca, obs.scale = 1, var.scale = 1, 
            groups = iris[,5], ellipse = TRUE, 
            circle = TRUE)
 g <- g + scale_color_discrete(name = '')
 g <- g + theme(legend.direction = 'horizontal', 
             legend.position = 'top')
  print(g)

我收到以下错误：

Installation failed: there is no package called ‘R6’
Error in library(ggbiplot) : there is no package called ‘ggbiplot’

我正在尝试在此演示https://www.r-bloggers.com/computing-and-visualizing-pca-in-r/之后执行一些 PCA 分析