使用R获取逗号之前的字符串

Question

我是R的初学者.现在,我在这样的data.frame中有一个向量

city
Kirkland,
Bethesda,
Wellington,
La Jolla,
Berkeley,
Costa, Evie KW172NJ
Miami,
Plano,
Sacramento,
Middletown,
Webster,
Houston,
Denver,
Kirkland,
Pinecrest,
Tarzana,
Boulder,
Westfield,
Fair Haven,
Royal Palm Beach, Fl
Westport,
Encino,
Oak Ridge,

我想清理它.我想要的是逗号之前的所有城市名称.如何在R中获得结果？谢谢!

Answer 1

你可以使用gsub一点正则表达式:

cities <- gsub("^(.*?),.*", "\\1", df$city)

这个也适用:

cities <- gsub(",.*$", "", df$city)

Answer 2

只是为了好玩，您可以使用strsplit

> x <- c("London, UK", "Paris, France", "New York, USA")
> sapply(strsplit(x, ","), "[", 1)
[1] "London"   "Paris"    "New York"