正则表达式过滤器的匿名函数

Question

我有一个filter()函数，它在tibble中过滤特定的Regex。因为我需要这样做不止一次，所以我想编写一个as_mapper()函数，最后得到更短的代码。我该怎么做？

我尝试了以下几点：

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)

如果我试图将这个函数添加到tibble中，R会抛出一个C stack usage x is too close to the limit错误。我怎么才能避免这种情况？

可以使用以下代码生成我想要检查的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

编辑以获得较短的代码

您可以编写一个不依赖于as_mapper的简单单行函数：

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")

这将只返回未找到regex的df行。

我不认为您需要在这里使用映射器，您可以简单地构建一个正常的函数，它将接受一个tibble、一个目标regex作为输入，并通过一个提供grepl结果的新增列来返回该数据。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