R:选择LIKE(grep)条件所在的位置

Question

我正在使用R.

我有以下数据：

library(fastLink)
a = data.frame(dfA)
head(a)
firstname middlename        lastname housenum          streetname          city birthyear
1    daniel     joseph          secuya     1564         fairview ct       Oakland      1957
2     david     marion      motakabbir     6909  shepherd ave apt 4       Oakland      1971
3    joseph      aaron          joseph     4547        piedmont ave Castro Valley      1948
4    joseph      clyde         mcnulty    30436            49th ave Castro Valley      1961
5 akensheye     nguyen paniagua chavez     6967         glenwood dr       Oakland      1972
6      john       <NA>          bozman     6363            nabor st     Livermore      1951

从这里开始，我试图从这个表中选择行；名字"；包含字母"；jo"；。我试着用"；grep"；命令：

a[grep("jo", a$firstname)] 
Error in `[.data.frame`(a, grep("jo", a$firstname)) : 
undefined columns selected

有人知道为什么会出现这个错误吗？

感谢

Answer 1

final = a[grep("cl", a$firstname),] 

这似乎已经解决了！谢谢大家！