从HTML表格中提取数据

Question

从HTML表格中提取数据

5

我正在尝试使用rvest包从CABI入侵物种百科全书中提取关于入侵植物物种位置的数据。通过查看一些教程，我已经知道可以相对容易地从表格中抓取数据。但是，我遇到了一些困难。假设我想获取Brassica tournefortii物种的位置数据。我应该能够使用下面的代码，该代码使用这里概述的技术来获取物种已被记录的位置的详细信息。

 library(rvest)
 isc<-read_html("http://www.cabi.org/isc/datasheet/50069")
 isc %>% 
 html_node("#toDistributionTable td:nth-child(1)") %>%
 html_text()

然而，运行此代码时我收到了错误。

Error: No matches

我完全不了解网络爬虫。我做错了什么吗？

- Phil_Martin

1个回答

网页内容由stack overflow 提供, 点击上面的

可以查看英文原文，
原文链接

- hrbrmstr · Accepted Answer

首先，我希望我能给你更多的赞。终于有一个与$SPORTSBALL或$MONEY无关的网络爬虫问题！ :-)

那个网站很恶劣。它使用嵌入式命名空间，需要处理，这也意味着需要使用xml2包：

library(rvest)
library(xml2)

isc <- read_html("http://www.cabi.org/isc/datasheet/50069")

ns <- xml_ns(isc)

xml_text(xml_find_all(isc, xpath="//div[@id='toDistributionTable']/table/tbody/tr/td[1]", ns))

##  [1] "ASIA"                           "Azerbaijan"                    
##  [3] "Bhutan"                         "China"                         
##  [5] "-Tibet"                         "India"                         
##  [7] "-Delhi"                         "-Indian Punjab"                
##  [9] "-Rajasthan"                     "-Uttar Pradesh"                
## [11] "Iran"                           "Iraq"                          
## [13] "Israel"                         "Jordan"                        
## [15] "Kuwait"                         "Lebanon"                       
## [17] "Oman"                           "Pakistan"                      
## [19] "Qatar"                          "Saudi Arabia"                  
## [21] "Syria"                          "Turkey"                        
## [23] "Turkmenistan"                   "United Arab Emirates"          
## [25] "Uzbekistan"                     "Yemen"                         
## [27] "AFRICA"                         "Algeria"                       
## [29] "Egypt"                          "Libya"                         
## [31] "Morocco"                        "South Africa"                  
## [33] "Tunisia"                        "NORTH AMERICA"                 
## [35] "Mexico"                         "USA"                           
## [37] "-Arizona"                       "-California"                   
## [39] "-Nevada"                        "-New Mexico"                   
## [41] "-Texas"                         "-Utah"                         
## [43] "SOUTH AMERICA"                  "Chile"                         
## [45] "EUROPE"                         "Belgium"                       
## [47] "Cyprus"                         "Denmark"                       
## [49] "France"                         "Greece"                        
## [51] "Ireland"                        "Italy"                         
## [53] "Spain"                          "Sweden"                        
## [55] "UK"                             "-England and Wales"            
## [57] "-Scotland"                      "OCEANIA"                       
## [59] "Australia"                      "-Australian Northern Territory"
## [61] "-New South Wales"               "-Queensland"                   
## [63] "-South Australia"               "-Tasmania"                     
## [65] "-Victoria"                      "-Western Australia"            
## [67] "New Zealand"