选择了未定义的列 - R.

Question

我从我应该做的练习中复制了这个。

BirdBrains <-read.csv("~/NTNU/ST0103/BirdBrains.csv")

Names <-c("Order", "Family", "Species.name.")
Variables <-c("Maximum.lifespan", "Age.at.first.reprodction", "Incubation.length",
              "Clutch.size", "Mean.latitude", "logBodyMass", "logBrainMass")
BirdClutch <- BirdBrains[,c(Names,Variables)]

我收到此错误消息：

Error in `[.data.frame`(BirdBrains, , c(Names, Variables)) : 
  undefined columns selected

谁能告诉我什么错了？