在第一个空格之前获取字符

Question

我正在寻找一种grep方法来获取第一个空格之前的字符串中的字符.

我已经破解了以下功能,因为我无法弄清楚如何使用grep类型命令来执行此操作R.

有人可以帮助grep解决方案 - 如果有的话......

beforeSpace <- function(inWords) {
    vapply(inWords, function(L) strsplit(L, "[[:space:]]")[[1]][1], FUN.VALUE = 'character')
}
words <- c("the quick", "brown dogs were", "lazier than quick foxes")
beforeSpace(words)

R>          the quick         brown dogs were lazier than quick foxes 
              "the"                 "brown"                "lazier" 

并且让我知道是否有比grep(或我的功能beforeSpace)更好的方法来做到这一点.

Answer 1

或者只是sub,归功于@flodel:

sub(" .*", "", words)
# and if the 'space' can also be a tab or other white-space:
sub("\\s.*","",words)
#[1] "the"    "brown"  "lazier"

Answer 2

您可以使用qdap's beg2char（字符串以特定字符开头），如下所示：

x <- c("the quick", "brown dogs were", "lazier than quick foxes")
library(qdap)
beg2char(x)
## [1] "the"    "brown"  "lazier"

Answer 3

使用stringi

library(stringi) 
stri_extract_first(words, regex="\\w+")
#[1] "the"    "brown"  "lazier"