我想将以下 xml 文档转换为可用于访问坐标信息的数据框。

a3 <- xmlParse("test.xml")

我想我必须执行某种应用函数，但我仍然不确定如何处理具有许多用于标识该特定节点的子节点的 xml 子节点。 <Marker_Data>和 <Marker>节点使用子节点和姐妹节点(分别)作为它们的唯一标识。这是一个简单的问题吗？我在堆栈溢出上看到的示例在每个级别都有唯一的 xml 属性来标识节点:示例 - Parsing XML with different number of subnode with same name in R或 Extract second attribute of a xml node in R (XML package)

我想制作这样的数据框:

| Filename | Type| Xaxis| Yaxis | Zaxis |

| File.tif |  1  | 7172 | 4332  |   1   |

| File.tif |  1  | 7170 | 4140  |   1   |

| File.tif |  2  | 6172 | 4332  |   1   |

| File.tif |  2  | 5173 | 4140  |   1   |

测试.XML:

<?xml version="1.0" encoding="UTF-8"?>
<CellCounter_Marker_File>
 <Image_Properties>
     <Image_Filename>File.tif</Image_Filename>
 </Image_Properties>
 <Marker_Data>
     <Marker_Type>
         <Type>1</Type>
         <Marker>
             <MarkerX>7172</MarkerX>
             <MarkerY>4332</MarkerY>
             <MarkerZ>1</MarkerZ>
         </Marker>
         <Marker>
             <MarkerX>7170</MarkerX>
             <MarkerY>4140</MarkerY>
             <MarkerZ>1</MarkerZ>
         </Marker>
     </Marker_Type>
     <Marker_Type>
         <Type>2</Type>
         <Marker>
             <MarkerX>6172</MarkerX>
             <MarkerY>4332</MarkerY>
             <MarkerZ>1</MarkerZ>
         </Marker>
         <Marker>
             <MarkerX>5173</MarkerX>
             <MarkerY>4140</MarkerY>
             <MarkerZ>1</MarkerZ>
         </Marker>
     </Marker_Type>
 </Marker_Data>
</CellCounter_Marker_File>

最佳答案

由于节点 Marker 是定义行的节点，因此您应该将它们用作循环的基础。获取 Marker-nodes 使用

xml_find_all(doc, ".//Marker")

然后您遍历标记节点，并使用 xpath 查找相关子节点(MarkerX、MarkerY 和 MarkerZ)，还要找到它的兄弟节点 (Type) 和祖先节点 (Image_Filename)... 一旦找到，xml_text() 用于提取它们的值。

代码

library( xml2 )
library( tidyverse )

df <-
  #get all markers, since thay are defining the rows
  xml_find_all(doc, ".//Marker") %>%
  #iterate over the markers, and get relevant data from child-, ancestor- and sibling-nodes
  map_df( function(x) {
    set_names( c( #get the filename, which is in the preceeding sibling 'Type' of the marker 
                  xml_find_all( x, "./ancestor::Marker_Data/preceding-sibling::Image_Properties/Image_Filename") %>% xml_text(),
                  #get the types, whoich are in the preceeding sibling 'Type' of the marker 
                  xml_find_all( x, "./preceding-sibling::Type") %>% xml_text(),
                  #get the MarkersX, Y and Z of the marker 
                  xml_find_all( x, ".//MarkerX") %>% xml_text(),
                  xml_find_all( x, ".//MarkerY") %>% xml_text(),
                  xml_find_all( x, ".//MarkerZ") %>% xml_text() ), 
               #set the column names
               c( "File", "Type", "Xaxis", "Yaxis", "z") ) %>% 
      as.list() %>% #make list
      flatten_df() #flatten to a data.frame
  }) %>%
  type_convert() #let R convert the values for you

输出

# # A tibble: 4 x 5
#   File      Type Xaxis Yaxis     z
#   <chr>    <int> <int> <int> <int>
# 1 File.tif     1  7172  4332     1
# 2 File.tif     1  7170  4140     1
# 3 File.tif     2  6172  4332     1
# 4 File.tif     2  5173  4140     1

样本数据

doc <- read_xml( '<?xml version="1.0" encoding="UTF-8"?>
<CellCounter_Marker_File>
<Image_Properties>
<Image_Filename>File.tif</Image_Filename>
</Image_Properties>
<Marker_Data>
<Marker_Type>
<Type>1</Type>
<Marker>
<MarkerX>7172</MarkerX>
<MarkerY>4332</MarkerY>
<MarkerZ>1</MarkerZ>
</Marker>
<Marker>
<MarkerX>7170</MarkerX>
<MarkerY>4140</MarkerY>
<MarkerZ>1</MarkerZ>
</Marker>
</Marker_Type>
<Marker_Type>
<Type>2</Type>
<Marker>
<MarkerX>6172</MarkerX>
<MarkerY>4332</MarkerY>
<MarkerZ>1</MarkerZ>
</Marker>
<Marker>
<MarkerX>5173</MarkerX>
<MarkerY>4140</MarkerY>
<MarkerZ>1</MarkerZ>
</Marker>
</Marker_Type>
</Marker_Data>
</CellCounter_Marker_File>' )

关于r - 将 XML 文档转换为 R 数据框，其中子节点都具有相同的名称并使用子节点进行标识，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/52751479/