R rvest:找不到函数"xpath_element". [英] R rvest: could not find function "xpath_element"

问题描述

我试图简单地复制rvest::html_nodes()的示例，但遇到错误:

I am trying to simply replicate the example of rvest::html_nodes(), yet encounter an error:

library(rvest)
ateam <- read_html("http://www.boxofficemojo.com/movies/?id=ateam.htm")
html_nodes(ateam, "center")

do.call(方法，列表(解析的选择器))中的错误:找不到 函数"xpath_element"

Error in do.call(method, list(parsed_selector)) : could not find function "xpath_element"

如果加载诸如httr，xml2，selectr之类的程序包，也会发生同样的情况.我似乎也有这些软件包的最新版本...

The same happens if I load packages such as httr, xml2, selectr. I seem to have the latest version of these packages too...

诸如xpath_element，xpath_combinedselector之类的功能位于哪些程序包中?我如何使它工作?请注意，我在Ubuntu 16.04上运行，因此该代码可能会在其他平台上运行...

In which packages are functions such as xpath_element, xpath_combinedselector located? How do I get it to work? Note that I am running on Ubuntu 16.04, so that code might work on other platforms...

推荐答案

我知道这个问题已经很久了，但是我想为可能有类似问题的人发表评论.

I understand this issue is rather old but I wanted to post a comment for those who may have similar issues.

我偶然发现了此错误，无法找到很多帮助.因此，我认为与其针对CSS，不如尝试针对xpath.我不知道最佳做法是什么.

I stumbled upon this same error and was unable to find much help. So, I thought instead of targeting CSS I would try to target the xpath instead. I do not know what the best practice is.

我的原始功能在Ubuntu 16，R 3.4.0上运行良好.但是，它们在Debian 8 R 3.3.3和R 3.4.0上失败.

My original functions worked fine on Ubuntu 16, R 3.4.0. However, they failed on Debian 8 R 3.3.3 and R 3.4.0.

当我将代码修改为以xpath而不是css为目标时，它们开始按预期工作.例如，更改此...

When I modified my code to target xpaths instead of css they began working as expected. For example, changing this...

contents <- link %>% 
    xml2::read_html() %>%
    rvest::html_nodes(css = "pre") %>%
    rvest::html_text()

对此...

contents <- link %>%
    xml2::read_html() %>%
    rvest::html_nodes(xpath = "//pre") %>%
    rvest::html_text()

解决了我的问题.

这篇关于R rvest:找不到函数"xpath_element".的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！