find_xml_all返回{xml_nodeset(0)}

我最近从这张地图下载了KML文件,并尝试使用该软件包xml2来提取露营地的信息,例如地理位置,站点周围的设施等; 但我{xml_nodeset (0)}到最后.

Belows是我用过的代码,

library(xml2)
campsites <- read_xml("file_path")
xml_find_all(campsites, ".//Placemark")

这是KML文件的结构(您也可以尝试xml_structure(campsites)),

> library(magrittr)
> campsites
{xml_document}

[1] \nWordPress & MapsMarker.com]] ...
>
> campsites %>% xml_children %>% xml_children %>% xml_children
{xml_nodeset (55)}
 [1] \n  \n    http://www.mountaineering-lohas.org/wp-content/uploads/leaflet-maps-marker-icons/tents.png\n  \n
 [2] \n  \n    http://www.mountaineering-lohas.org/wp-content/uploads/leaflet-maps-marker-icons/tents-1.png\n  \n
 [3] \n  \n    http://www.mountaineering-lohas.org/wp-content/uploads/leaflet-maps-marker-icons/tents1.png\n  \n
 [4] 香港營地 Hong Kong Camp Site
 [5] \n#tents\næµæ°´éŸ¿ç‡Ÿåœ° ( Lau Shui Heung Camp Site )\n2013-02-21T04:02:29+08: ...
 [6] \n#tents\n鶴藪營地(Hok Tau Camp Site)\n2013-02-21T04:02:18+08:00\n#tents\n涌背營地(Chung Pui Camp Site)\n2013-02-22T11:02:02+08:00\n#tents\næ±å¹³æ´²ç‡Ÿåœ° (Tung Ping Chau Campsite)\n2013-02-22T11:02:39+08:00\n#tents\nç£ä»”å—營地(Wan Tsai Peninsula South Campsite)\n2013-02-22T11:02:2 ...
[10] \n#tents\nç£ä»”西營地 (Wan Tsai Peninsula West Campsite)\n2013-02-22T11:02:3 ...
...

正如您所看到的,有一些名为"Placemark"的节点,为什么我找不到使用的节点xml_find_all？我的代码中是否有任何错误？

谢谢!

看起来你有一些名称空间.如果将前缀添加到xpath,则可以获取节点集.

xml_ns(campsites)
# d1   <-> http://www.opengis.net/kml/2.2
# atom <-> http://www.w3.org/2005/Atom
# gx   <-> http://www.google.com/kml/ext/2.2

xml_find_all(campsites, ".//d1:Placemark", xml_ns(campsites))
# {xml_nodeset (45)}
#  [1] \n#tents\n????? ( La ...
#  [2] \n#tents\n????(Hok T ...
#  ...

要获取cdata中的文本,您可以使用类似的内容

xml_text(xml_find_all(campsites, "//d1:description", xml_ns(campsites))) 
# or "//d1:description/text()"