r - 在 R 中，在字符串数据框列中的 % 符号之前提取数字值

Question

在下面的数据框中，我正在尝试构建一个新列“avcomp”，如果 duty_nature 是“M”或“C”，它会从“code”列中提取空格和 % 符号之间的数值.我尝试了下面的代码，但它只能获得前两个数字和百分号。你能帮忙吗？

avcomp 列应该是

>[1] "30", "0.50, ""

谢谢!

code <- c("Greater than 30% of something","Less than 0.50% of something","30%")
duty_nature<- c("M","C","A")
test <-data.frame(code,duty_nature)
  
test$avcomp <- ifelse(test$duty_nature == "M" | test$duty_nature == "C",str_sub(str_match(test$code,"\\s*(.*?)%\\s*"),-4,-1),"")

Answer 1

正则表达式模式 [0-9]+[.]?[0-9]*(?=%) 匹配小数点后跟百分号的任何数字(向前看):

library(tidyverse)
code <- c("Greater than 30% of something", "Less than 0.50% of something", "30%")
duty_nature <- c("M", "C", "A")
test <- data.frame(code, duty_nature)

test %>%
  mutate(
    avcomp = ifelse(
      duty_nature %in% c("M", "C"),
      code %>% str_extract("[0-9]+[.]?[0-9]*(?=%)") %>% as.numeric(),
      NA
    )
  )
#>                            code duty_nature avcomp
#> 1 Greater than 30% of something           M   30.0
#> 2  Less than 0.50% of something           C    0.5
#> 3                           30%           A     NA

^{由 reprex package 创建于 2022-03-21 (v2.0.0)}