R:删除字符串开头和结尾的数字 [英] R: removing numbers at begin and end of a string

问题描述

我有以下向量:

words <- c("5lang","kasverschil2","b2b")

我想删除 "5lang" 中的 "5" 和 "kasverschil2" 中的 "2".但我不想删除 "b2b" 中的 "2".

I want to remove "5" in "5lang" and "2" in "kasverschil2". But I do NOT want to remove "2" in "b2b".

推荐答案

 gsub("^\\d+|\\d+$", "", words)    
 #[1] "lang"        "kasverschil" "b2b"

另一种选择是使用 stringi

 library(stringi)
 stri_replace_all_regex(words, "^\\d+|\\d+$", "")
  #[1] "lang"        "kasverschil" "b2b"        

此处使用 OP 提供的数据集的变体是 3 种主要解决方案的基准测试(请注意，这些字符串非常短且人为设计；结果在更大的真实数据集上可能会有所不同):

Using a variant of the data set provided by the OP here are benchmarks for 3 three main solutions (note that these strings are very short and contrived; results may differ on a larger, real data set):

words <- rep(c("5lang","kasverschil2","b2b"), 100000)

library(stringi)
library(microbenchmark)

GSUB <- function() gsub("^\\d+|\\d+$", "", words)
STRINGI <- function() stri_replace_all_regex(words, "^\\d+|\\d+$", "")
GREGEXPR <- function() {
    gregexpr(pattern='(^[0-9]+|[0-9]+$)', text = words) -> mm
    sapply(regmatches(words, mm, invert=TRUE), paste, collapse="") 
}

microbenchmark( 
    GSUB(),
    STRINGI(),
    GREGEXPR(),
    times=100L
)

## Unit: milliseconds
##        expr       min        lq    median        uq       max neval
##      GSUB()  301.0988  349.9952  396.3647  431.6493  632.7568   100
##   STRINGI()  465.9099  513.1570  569.1972  629.4176  738.4414   100
##  GREGEXPR() 5073.1960 5706.8160 6194.1070 6742.1552 7647.8904   100

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