PDF抓取：获取公司和子公司表

Question

我正在尝试抓取包含有关公司子公司信息的 PDF。我看过很多使用 R 包 Tabulizer 的帖子，但不幸的是，由于某些原因，这在我的 Mac 上不起作用。由于 Tabulizer 使用 Java 依赖项，因此我尝试安装不同版本的 Java (6-13)，然后重新安装软件包，但仍然无法正常工作（当我运行 extract_tables R 会话中止时会发生什么）。

我需要从第 19 页开始抓取整个 pdf，并构建一个显示公司名称及其子公司的表格。在 pdf 中，名称以任何字母/数字/符号开头，而子公司则以单点或双点开头。

所以我尝试了pdftools 和pdftables 包。下面的代码提供了一个类似于第 19 页的表格：

library(pdftools)
library(pdftables)
library(tidyverse)

tt = pdf_text("~/DATA/978-1-912036-41-7-Who Owns Whom UK-Ireland-Volume-1.pdf")

df <- tt[19]
df2 <- strsplit(df, '  ')
 
df3 <-as.data.frame(do.call(cbind, df2)) %>% 
 filter(V1!="") %>% 
 mutate(V2=str_split_fixed(V1, "England . ", 2)) %>% 
 mutate(V3=str_split_fixed(V1, "England", 2)) %>% 
 select(V2,V3,V1) %>% 
 mutate(V1=ifelse(V1==V3,"",V1),V3=ifelse(V3==V2,"",V3)) %>% 
 select(V3,V2,V1) %>% 
 mutate_at(c("V1"), funs(lead), n = 1 ) %>% 
 mutate_at(c("V3"), funs(lag), n = 1 ) %>% 
 unite(V4,V1, V2, V3, sep = "", remove = FALSE)

我确信有一个更复杂的功能可以更巧妙地完成这项工作。例如使用'\n' 或'\r' 和strsplit：

 df2 <- strsplit(df, '\n') 
 df3 <- do.call(cbind.data.frame, df2)

谁能告诉我如何刮这张桌子？

Answer 1

就像@Justin Coco 暗示的那样，这很有趣。代码最终比我预期的要复杂一些，但我认为结果应该是你想象的那样。

我使用了pdf_data 而不是pdf_text，所以我可以处理单词的位置。

library(pdftools)
#> Using poppler version 0.86.1
library(tidyverse)
pdf_location <- "/location/of/pdf"
pdf_raw <- pdf_data(pdf_location)

然后我编写了一个可以处理 PDF 页面的函数：

get_table <- function(x, page) {
  x[[page]] %>% # select page, I use this variable again below, which is why I'm not simply looping through the whole object

    filter(y > 25, y < 833) %>% # above and below these positions is the pdf header which we are not interested in
    mutate(column = case_when( # I check the x-positions where the columns start an end and transformed them into column numbers
      x >= 36 & x < 220 ~ 1L,
      x >= 220 & x < 403 ~ 2L,
      x >= 403 ~ 3L,
    )) %>% 
    mutate(newrow = case_when( # check if this is a new line
      column == 1L & x == 36  ~ TRUE, 
      column == 2L & x == 220 ~ TRUE,
      column == 3L & x == 403 ~ TRUE,
      TRUE ~ FALSE
    ),
    row = cumsum(newrow), # get the row number
    subsidiary = newrow & text == ".") %>% # as you say, subsidiary names start with "."
    group_by(row, column) %>% # grouping and summarising moves the text into one 'cell'
    summarise(text = paste(text, collapse = " "), 
              subsidiary = sum(subsidiary) > 0,
              .groups = "drop") %>% 
    mutate(headline = !str_detect(text, "\\s")) %>% # the category headlines (@, A, B, C, etc.) are still in there but can be identified easily since they lack whitespace
    mutate(row = ifelse(row > 1 & !subsidiary & !lag(subsidiary) & !lag(headline), lag(row), row),
           row = ifelse(row > 1 & !subsidiary & !lag(subsidiary) & !lag(headline), lag(row), row)) %>% # some company names stretch over up to three lines but lines are not indented
    group_by(row, column) %>% 
    summarise(text = paste(text, collapse = " "), 
              subsidiary = sum(subsidiary) > 0,
              headline = head(headline, 1),
              .groups = "drop")  %>% 
    
    mutate(page = page, .before = row) # finally add the page number to keep track
}

您可以在一个页面上进行测试，也可以一次循环浏览所有页面：

pdf_df <- map_df(19:1428, ~get_table(pdf_raw, page = .x))  

我已经喜欢 df，但您要求表格应该是“显示公司名称及其子公司”。因此，让我们对pdf_df 对象进行更多争论。

pdf_df %>% 
  filter(!headline) %>% 
  mutate(company_nr = cumsum(!subsidiary)) %>% 
  group_by(company_nr) %>% 
  mutate(company = text[!subsidiary & !headline]) %>% 
  filter(subsidiary) %>% 
  select(company_nr, company, subsidiary = text)
#> # A tibble: 303,380 x 3
#> # Groups:   company_nr [115,477]
#>    company_nr company                             subsidiary                    
#>         <int> <chr>                               <chr>                         
#>  1          1 ?WHAT IF! HOLDINGS LIMITED The Gla… . ?What If! China Holdings Li…
#>  2          1 ?WHAT IF! HOLDINGS LIMITED The Gla… . . ?What If! Innovation Sing…
#>  3          1 ?WHAT IF! HOLDINGS LIMITED The Gla… . ?What If! Joint Ventures Li…
#>  4          1 ?WHAT IF! HOLDINGS LIMITED The Gla… . ?What If! Limited England   
#>  5          1 ?WHAT IF! HOLDINGS LIMITED The Gla… . . ? What If ! Inventors Lim…
#>  6          1 ?WHAT IF! HOLDINGS LIMITED The Gla… . . ? What If ! Training Limi…
#>  7          1 ?WHAT IF! HOLDINGS LIMITED The Gla… . Nobby Styles Limited Englan…
#>  8          2 @A COMPANY LIMITED Premier Suite 4… . Aviva Holdings Limited Engl…
#>  9          2 @A COMPANY LIMITED Premier Suite 4… . Copper Mountain Networks Li…
#> 10          2 @A COMPANY LIMITED Premier Suite 4… . Just Ties Limited England   
#> # … with 303,370 more rows

^{由reprex package (v2.0.0) 于 2021 年 5 月 23 日创建}

如果有问题，请在评论中告诉我。我显然没有浏览所有页面来检查脚本是否有一些与特定公司名称等有关的怪癖，但第一页对我来说看起来不错。