将 xml_nodeset 转换为 data.frame [英] Convert xml_nodeset to data.frame
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问题描述
我正在使用 rvest.我想将结果转换为数据框:
I am using rvest. And I would like to convert the result to a data frame:
> links <- pgsession %>% jump_to(urls[2]) %>% read_html() %>% html_nodes("a")
> links
{xml_nodeset (114)}
[1] <a href="/Mitglieder/Detail/1213412">Date</a>
[2] <a href="/Account/ChangePassword">Kennwort ändern</a>
[3] <a href="/Account/BenutzernamenAendern/124312234">Benutzernamen ändern</a>
[4] <a href="/Account/LogOff">Abmelden</a>
...
我使用了以下方法:
library(plyr)
ldply(xmlToList(links), data.frame)
Error in UseMethod("xmlSApply") :
no applicable method for 'xmlSApply' applied to an object of class "xml_nodeset"
df1 <- data.frame(character(13000))
df1 <- rbind(df1, data.frame(links ))# append to data.frame
但是，我收到一个错误:
However, I get an error:
Error in UseMethod("xmlSApply") :
no applicable method for 'xmlSApply' applied to an object of class "xml_nodeset"
任何建议我做错了什么?
Any suggestion what I am doing wrong?
感谢您的回复！
推荐答案
这将使您从链接中获得所有属性到 tbl_df.bind_rows 让你免费填充":
This will get you all the attributes from the links into a tbl_df. bind_rows gets you "fill" for free:
library(rvest)
library(dplyr)
pg <- read_html("https://en.wikipedia.org/wiki/Main_Page")
links <- html_nodes(pg, "a")
bind_rows(lapply(xml_attrs(links), function(x) data.frame(as.list(x), stringsAsFactors=FALSE)))
## Source: local data frame [310 x 10]
##
## id href title class dir accesskey rel lang hreflang style
## (chr) (chr) (chr) (chr) (chr) (chr) (chr) (chr) (chr) (chr)
## 1 top NA NA NA NA NA NA NA NA NA
## 2 NA #mw-head NA NA NA NA NA NA NA NA
## 3 NA #p-search NA NA NA NA NA NA NA NA
## 4 NA /wiki/Wikipedia Wikipedia NA NA NA NA NA NA NA
## 5 NA /wiki/Free_content Free content NA NA NA NA NA NA NA
## 6 NA /wiki/Encyclopedia Encyclopedia NA NA NA NA NA NA NA
## 7 NA /wiki/Wikipedia:Introduction Wikipedia:Introduction NA NA NA NA NA NA NA
## 8 NA /wiki/Special:Statistics Special:Statistics NA NA NA NA NA NA NA
## 9 NA /wiki/English_language English language NA NA NA NA NA NA NA
## 10 NA /wiki/Portal:Arts Portal:Arts NA NA NA NA NA NA NA
## .. ... ... ... ... ... ... ... ... ... ...
或者，您可以使用 purrr:
library(rvest)
library(purrr)
pg <- read_html("https://en.wikipedia.org/wiki/Main_Page")
html_nodes(pg, "a") %>%
map(xml_attrs) %>%
map_df(~as.list(.))
## # A tibble: 342 × 10
## id href title class dir accesskey rel hreflang lang style
## <chr> <chr> <chr> <chr> <chr> <chr> <chr> <chr> <chr> <chr>
## 1 top <NA> <NA> <NA> <NA> <NA> <NA> <NA> <NA> <NA>
## 2 <NA> #mw-head <NA> <NA> <NA> <NA> <NA> <NA> <NA> <NA>
## 3 <NA> #p-search <NA> <NA> <NA> <NA> <NA> <NA> <NA> <NA>
## 4 <NA> /wiki/Wikipedia Wikipedia <NA> <NA> <NA> <NA> <NA> <NA> <NA>
## 5 <NA> /wiki/Free_content Free content <NA> <NA> <NA> <NA> <NA> <NA> <NA>
## 6 <NA> /wiki/Encyclopedia Encyclopedia <NA> <NA> <NA> <NA> <NA> <NA> <NA>
## 7 <NA> /wiki/Wikipedia:Introduction Wikipedia:Introduction <NA> <NA> <NA> <NA> <NA> <NA> <NA>
## 8 <NA> /wiki/Special:Statistics Special:Statistics <NA> <NA> <NA> <NA> <NA> <NA> <NA>
## 9 <NA> /wiki/English_language English language <NA> <NA> <NA> <NA> <NA> <NA> <NA>
## 10 <NA> /wiki/Portal:Arts Portal:Arts <NA> <NA> <NA> <NA> <NA> <NA> <NA>
## # ... with 332 more rows
我认为这在功能上更符合习惯，而且是一种整体上更简洁的方法.
which I think is more functionally idiomatic and an overall cleaner approach.
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