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如何使用xml2和purrr在不同级别提取xml\U属性和xml\U文本?

xml2 purrr tidyverse dplyr r

2

kabr hrbrmstr · 技术社区 · 8 年前

我想从XML文件中提取信息并将其转换为数据帧。

信息以XML文本和XML属性的形式存储在嵌套节点中:

结构示例:

<xmlnode node-id = "Text about xmlnode">
    <xmlsubnode subnode-id = "123">
        <xmlsubsubnode>
            I want to extract this text
        </xmlsubsubnode>
        <xmlsubsubnode>
            I want to extract this text
        </xmlsubsubnode>    
        <xmlsubsubnode>
            I want to extract this text
        </xmlsubsubnode>    
        <xmlsubsubnode>
            I want to extract this text
        </xmlsubsubnode>    
    </xmlsubnode>
    <xmlsubnode subnode-id = "456">
        <xmlsubsubnode>
            I want to extract this text
        </xmlsubsubnode>
        <xmlsubsubnode>
            I want to extract this text
        </xmlsubsubnode>    
        <xmlsubsubnode>
            I want to extract this text
        </xmlsubsubnode>    
        <xmlsubsubnode>
            I want to extract this text
        </xmlsubsubnode>    
    </xmlsubnode>
</xmlnode>
<xmlnode node-id = "Text about xmlnode">
    <xmlsubnode subnode-id = "123">
        <xmlsubsubnode>
            I want to extract this text
        </xmlsubsubnode>
        <xmlsubsubnode>
            I want to extract this text
        </xmlsubsubnode>    
        <xmlsubsubnode>
            I want to extract this text
        </xmlsubsubnode>    
        <xmlsubsubnode>
            I want to extract this text
        </xmlsubsubnode>    
    </xmlsubnode>
    <xmlsubnode subnode-id = "456">
        <xmlsubsubnode>
            I want to extract this text
        </xmlsubsubnode>
        <xmlsubsubnode>
            I want to extract this text
        </xmlsubsubnode>    
        <xmlsubsubnode>
            I want to extract this text
        </xmlsubsubnode>    
        <xmlsubsubnode>
            I want to extract this text
        </xmlsubsubnode>    
    </xmlsubnode>
</xmlnode>

我想获得以下信息:

* node-id (attribute)
* subnode-id (attribute)
* text in `xmlsubnodenode` (text)

我需要这样的长格式数据框:

node-id subnode-id  text
Text about xmlnode 1    123 I want to extract this text
Text about xmlnode 1    123 I want to extract this text
Text about xmlnode 1    123 I want to extract this text
Text about xmlnode 1    123 I want to extract this text
Text about xmlnode 1    456 I want to extract this text
Text about xmlnode 1    456 I want to extract this text
Text about xmlnode 1    456 I want to extract this text
Text about xmlnode 1    456 I want to extract this text
Text about xmlnode 2    123 I want to extract this text
Text about xmlnode 2    123 I want to extract this text
Text about xmlnode 2    123 I want to extract this text
Text about xmlnode 2    123 I want to extract this text
Text about xmlnode 2    456 I want to extract this text
Text about xmlnode 2    456 I want to extract this text
Text about xmlnode 2    456 I want to extract this text
Text about xmlnode 2    456 I want to extract this text

我试着跟随Jenny Bryans的方法 "How to tame XML with nested data frames and purrr" ,但它仅在第一个级别上起作用。

xml <- xml2::read_xml("input/example.xml")
rows <- 
  xml %>%
  xml_find_all("//xmlnode")
rows_df <- data_frame(row = seq_along(rows), nodeset = rows)
rows_df %>%
  mutate(node_id = nodeset %>% map(~ xml_attr(., "node-id"))) %>%
  select(row, node_id) %>%
  unnest()

你有什么想法来获取这些信息吗 purrr ?

1 回复 | 直到 8 年前

1

5

Felix Ebert 8 年前

一种不需要将行展开/添加到另一个数据帧的方法:为每个数据帧创建一个包含一行的数据帧 subsubnode 使用 purrr 连同 xml2 选择和提取 xmlsubnode 父级和 xmlnode 祖宗

工作样本:

library(dplyr)
library(xml2)
library(purrr)
library(tidyr)
xml <- xml2::read_xml("input/example.xml")
rows <- xml %>% xml_find_all("//xmlsubsubnode")
rows_df <- data_frame(node = rows) %>%
  mutate(node_id = node %>% map(~ xml_find_first(., "ancestor::xmlnode")) %>% map(~ xml_attr(., "node-id"))) %>%
  mutate(subnode_id = node %>% map(~ xml_parent(.)) %>% map(~ xml_attr(., "subnode-id"))) %>%
  mutate(text = node %>% map(~ xml_text(.))) %>%
  select(-node)