> foo<-read.table("C:/Users/Administrator/Desktop/foo.txt",header=T)
Warning message:
In read.table("C:/Users/Administrator/Desktop/foo.txt", header = T) :  incomplete final line found by readTableHeader on 'C:/Users/Administrator/Desktop/foo.txt'
主要原因是最后一行没有换行，打开数据文件foo.txt并在末行敲回车就可以解决了，具体运行过程如下：
敲回车前：
> foo<-read.table("C:/Users/Administrator/Desktop/foo.txt",header=T)
Warning message:
In read.table("C:/Users/Administrator/Desktop/foo.txt", header = T) :
  incomplete final line found by readTableHeader on 'C:/Users/Administrator/Desktop/foo.txt'
> foo
  treat weight
1     A    3.4
2     B     NA
3     A    5.8
敲回车后：
> foo<-read.table("C:/Users/Administrator/Desktop/foo.txt",header=T)
> foo
  treat weight
1     A    3.4
2     B     NA

3     A    5.8