Equivalent of which in scraping?

Question

I\'m trying to run some scraping where the action I take on a node is conditional on the contents of the node.

This should be a minimal example:

XML          


        

Answer 1

Based on R Conditional evaluation when using the pipe operator %>%, you can do something like

page %>% 
   html_nodes(xpath='//td[@class="id-tag"]') %>% 
   {ifelse(is.na(html_node(.,xpath="span")), 
           html_text(.),
           {html_node(.,xpath="span") %>% html_attr("title")}
   )}

I think it is possibly simple to discard the pipe and save some of the objects created along the way

nodes <- html_nodes(page, xpath='//td[@class="id-tag"]')
text <- html_text(nodes)
title <- html_attr(html_node(nodes,xpath='span'),"title")
value <- ifelse(is.na(html_node(nodes, xpath="span")), text ,title)

An xpath only approach might be

page %>% 
 html_nodes(xpath='//td[@class="id-tag"]/span/@title|//td[@class="id-tag"][not(.//span)]') %>%
 html_text()

Answer 2

An alternate approach:

library(tidyverse)
library(rvest)

XML <- '
<td class="id-tag">
    <span title="Really Long Text">Really L...</span>
</td>
<td class="id-tag">Short</td>
'

pg <- read_html(XML)

html_nodes(pg, "td[class='id-tag']") %>%
  map_chr(function(x) {
    if (xml_find_first(x, "boolean(.//span)")) {
      x <- html_nodes(x, xpath=".//span/@title")
    }
    html_text(x)
  })

## [1] "Really Long Text" "Short"