问题
I am new to rvest. How do I extract those elements with 2 class names or only 1 class name in tag?
This is my code and issue:
doc <- paste("<html>",
"<body>",
"<span class='a1 b1'> text1 </span>",
"<span class='b1'> text2 </span>",
"</body>",
"</html>"
)
library(rvest)
read_html(doc) %>% html_nodes(".b1") %>% html_text()
#output: text1, text2
#what i want: text2
#I also want to extract only elements with 2 class names
read_html(doc) %>% html_nodes(".a1 .b1") %>% html_text()
# Output that i want: text1
This is my machine spec:
Operation System: Windows 10.
rvest version: 0.3.2
R version 3.3.3 (2017-03-06)
Platform: x86_64-w64-mingw32/x64 (64-bit)
Running under: Windows >= 8 x64 (build 9200)
Anybody can help?
回答1:
You can use css selector as follows:
Select class contains b1 not a1:
read_html(doc) %>% html_nodes(".b1:not(.a1)")
# {xml_nodeset (1)}
# [1] <span class="b1"> text2 </span>
Or use the attribute selector:
read_html(doc) %>% html_nodes("[class='b1']")
# {xml_nodeset (1)}
# [1] <span class="b1"> text2 </span>
Select class contains both:
read_html(doc) %>% html_nodes(".a1.b1")
# {xml_nodeset (1)}
# [1] <span class="a1 b1"> text1 </span>
来源：https://stackoverflow.com/questions/45450981/rvest-scrape-2-classes-in-1-tag