# Base example
m = c("   name: aaaaaa, bbbbbb  age: 25" ,
      "age 34   person: aaaa, bbbb",
      " location: A  name aaaa, bbbbbbb")

# This function implement the solution
extract_lastfirst <- function(x) {
  stopifnot(`"{stringr} is required"` = requireNamespace("stringr"))

  stringr::str_extract(x, "\\w+, \\w+") # This line solve the problem
}
extract_lastfirst(m)
#> [1] "aaaaaa, bbbbbb" "aaaa, bbbb"     "aaaa, bbbbbbb"

# In the text there is a mention to "the first occurrence of", so try
# the solution with an example the have a "second" occurrence.
n <- c("name: aa, bb wrong: cc, dd")
extract_lastfirst(n)
#> [1] "aa, bb"



# formal tests for the solution ---------------------------------------
# (no output means test passed)

library(testthat)

testthat::test_that("goal achieved", {
  expected_out_m <- c("aaaaaa, bbbbbb", "aaaa, bbbb", "aaaa, bbbbbbb")
  expect_equal(extract_lastfirst(m), expected_out_m)
})

testthat::test_that("multiple occurrences", {
  expected_out_n <- c("aa, bb")
  expect_equal(extract_lastfirst(n), expected_out_n)
})

字符串
创建于2020-09-02由reprex package（v0.3.0）

devtools::session_info()
#> ─ Session info ───────────────────────────────────────────────────────────────
#>  setting  value                       
#>  version  R version 4.0.2 (2020-06-22)
#>  os       Ubuntu 20.04.1 LTS          
#>  system   x86_64, linux-gnu           
#>  ui       X11                         
#>  language (EN)                        
#>  collate  en_US.UTF-8                 
#>  ctype    en_US.UTF-8                 
#>  tz       Europe/Rome                 
#>  date     2020-09-02                  
#> 
#> ─ Packages ───────────────────────────────────────────────────────────────────
#>  package     * version date       lib source        
#>  assertthat    0.2.1   2019-03-21 [1] CRAN (R 4.0.2)
#>  backports     1.1.9   2020-08-24 [1] CRAN (R 4.0.2)
#>  callr         3.4.3   2020-03-28 [1] CRAN (R 4.0.2)
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#>  crayon        1.3.4   2017-09-16 [1] CRAN (R 4.0.2)
#>  desc          1.2.0   2018-05-01 [1] CRAN (R 4.0.2)
#>  devtools      2.3.1   2020-07-21 [1] CRAN (R 4.0.2)
#>  digest        0.6.25  2020-02-23 [1] CRAN (R 4.0.2)
#>  ellipsis      0.3.1   2020-05-15 [1] CRAN (R 4.0.2)
#>  evaluate      0.14    2019-05-28 [1] CRAN (R 4.0.2)
#>  fansi         0.4.1   2020-01-08 [1] CRAN (R 4.0.2)
#>  fs            1.5.0   2020-07-31 [1] CRAN (R 4.0.2)
#>  glue          1.4.2   2020-08-27 [1] CRAN (R 4.0.2)
#>  highr         0.8     2019-03-20 [1] CRAN (R 4.0.2)
#>  htmltools     0.5.0   2020-06-16 [1] CRAN (R 4.0.2)
#>  knitr         1.29    2020-06-23 [1] CRAN (R 4.0.2)
#>  magrittr      1.5     2014-11-22 [1] CRAN (R 4.0.2)
#>  memoise       1.1.0   2017-04-21 [1] CRAN (R 4.0.2)
#>  pkgbuild      1.1.0   2020-07-13 [1] CRAN (R 4.0.2)
#>  pkgload       1.1.0   2020-05-29 [1] CRAN (R 4.0.2)
#>  prettyunits   1.1.1   2020-01-24 [1] CRAN (R 4.0.2)
#>  processx      3.4.3   2020-07-05 [1] CRAN (R 4.0.2)
#>  ps            1.3.4   2020-08-11 [1] CRAN (R 4.0.2)
#>  R6            2.4.1   2019-11-12 [1] CRAN (R 4.0.2)
#>  remotes       2.2.0   2020-07-21 [1] CRAN (R 4.0.2)
#>  rlang         0.4.7   2020-07-09 [1] CRAN (R 4.0.2)
#>  rmarkdown     2.3     2020-06-18 [1] CRAN (R 4.0.2)
#>  rprojroot     1.3-2   2018-01-03 [1] CRAN (R 4.0.2)
#>  sessioninfo   1.1.1   2018-11-05 [1] CRAN (R 4.0.2)
#>  stringi       1.4.6   2020-02-17 [1] CRAN (R 4.0.2)
#>  stringr       1.4.0   2019-02-10 [1] CRAN (R 4.0.2)
#>  testthat    * 2.3.2   2020-03-02 [1] CRAN (R 4.0.2)
#>  usethis       1.6.1   2020-04-29 [1] CRAN (R 4.0.2)
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#>  xfun          0.16    2020-07-24 [1] CRAN (R 4.0.2)
#>  yaml          2.2.1   2020-02-01 [1] CRAN (R 4.0.2)
#> 
#> [1] /home/cl/R/x86_64-pc-linux-gnu-library/4.0
#> [2] /usr/local/lib/R/site-library
#> [3] /usr/lib/R/site-library
#> [4] /usr/lib/R/library

型

您的正则表达式似乎不完全正确。请尝试使用[A-Za-z]+,\s[A-Za-z]+，看看是否有区别。语句开头的插入符号只会匹配行首模式开始的字符串，最后的美元符号只会匹配在行的最后结束的模式。我还将A-Z和a-z组合成一组，删除了一个不必要的反斜杠。将来用RegExr之类的东西测试你的正则表达式可能会很有帮助，它可以保存很多重复运行程序的痛苦。