in read.table(file = file, header = header, sep

> tab<- read.csv("data.csv",header = TRUE,stringsAsFactors = F,na.strings = "")

Warning messages:

1: In read.table(file = file, header = header, sep = sep, quote = quote, :

line 1 appears to contain embedded nulls

2: In read.table(file = file, header = header, sep = sep, quote = quote, :

incomplete final line found by readTableHeader on 'data.csv'

原因：偷懒，直接将Excel文件复制粘贴，再修改这个副本文件后缀为.csv

解决：打开Excel文件另存为.csv格式