正则表达式过滤器的匿名函数

Question

我有一个 filter() 函数，用于过滤 tibble 中的特定正则表达式。因为我需要多次执行此操作，所以我想编写一个 as_mapper() 函数以得到更短的代码。我该怎么做？

我尝试了以下方法：

adverts <- as_mapper(~!grepl("(xtm)|((k|K)(i|I|1|11)(d|D)(n|N).)|(Ar<e)\\s(you)\\s(in)| 
  (LOAN)|(AR(\\s|\\S)[0-9])|((B|b)(i|1|l)tc.)|(Coupon)|(Plastic.King)|(organs)|(SILI)|(Electric.Cigarette.Machine)",.$value,perl = T)%>% filter)

如果我尝试将此函数添加到 tibble，R 会抛出 C stack usage x is too close to the limit 错误。我怎样才能避免这种情况？

可以使用以下代码生成我要检查的 tibble 之一：

library(tidyverse)
library(rvest)
library(textreadr)

bribe <- read_html(paste("http://ipaidabribe.com/reports/paid?page", 10, sep = "="))
all.nodes <- c(".heading-3 a",".paid-amount span", ".date", ".location", ".transaction a")
test <- map(all.nodes, ~ html_nodes(bribe, .x) %>% html_text()) %>% 
  unlist %>% 
  as_tibble
adverts(test)

Answer 1

编辑更短的代码

你可以写一个不依赖as_mapper的简单的一行函数：

target_regex <- "(xtm)|((k|K)(i|I|1|11)(d|D)(n|N).)|(Ar<e)\\s(you)\\s(in)| 
(LOAN)|(AR(\\s|\\S)[0-9])|((B|b)(i|1|l)tc.)|(Coupon)|(Plastic.King)|(organs)|(SILI)|(Electric.Cigarette.Machine)"
adverts <- function(df, col) df[!grepl(target_regex, df[[col]],perl = T), ]
test_df %>% adverts(col = "value")

这将只返回 df 中找不到正则表达式的行

---

我认为您不需要在这里使用映射器，您可以简单地构建一个普通函数，该函数将一个 tibble、一个目标正则表达式作为输入，并返回该 tibble 并添加一个列，给出grepl 的结果。一种可能是：

filter_regex <- function(df, regex, col){
    df %>% 
        mutate(found = grepl(pattern = regex, x = df[[col]])) %>% 
        filter(found == TRUE) %>% 
        select(-found)
}
test_df <- map(all.nodes, ~ html_nodes(bribe, .x) %>% html_text()) %>%
    unlist %>% 
    as_tibble
target_regex <- "(xtm)|((k|K)(i|I|1|11)(d|D)(n|N).)|(Ar<e)\\s(you)\\s(in)| 
(LOAN)|(AR(\\s|\\S)[0-9])|((B|b)(i|1|l)tc.)|(Coupon)|(Plastic.King)|(organs)|(SILI)|(Electric.Cigarette.Machine)"

filter_regex(test_df, target_regex, "value")

> # A tibble: 7 x 1
>  value                                                                                      
>  <chr>                                                                                      
> 1 "\r\n                      Kidney Donor Needed Urgently Needed\r\n                    "    
> 2 "\r\n                      Kidney Donor Needed Urgetly \r\n                    "           
> 3 "\r\n                      Urgent Kidney Donor Needed\r\n                    "             
> 4 "\r\n                      Urgent Kidney Donor Needed\r\n                    "             
> 5 "\r\n                      Kidney Donor Needed\r\n                    "                    
> 6 "\r\n                      Kidney Donor Needed\r\n                    "                    
> 7 "\r\n                      Kidney donation urgently needed in India for 7 CR\r\n