使用rgdal中的writeOGR（）</styleurl> </name>时，在.kml中协助<name>和<styleurl>

Question

我有一个数据框，其中包含我想要与Google地球一起使用的各种位置的坐标。这是一个显示结构的简单示例：

data <- data.frame(country = "USA", city = "Saint Paul",
                   lat = 44.9629, lon = -93.00146)

我跟着this SO post和this guide使用KML包中的writeOGR()函数成功创建rgdal输出，但是我无法调整属性。这是代码：

# you may need to install gdal itself for the package to install successfully
# install.packages("rgdal")
library(rgdal)
data_sp <- data
coordinates(data_sp) <- c("lon", "lat")
proj4string(data_sp) <- CRS("+init=epsg:4238")
data_ll <- spTransform(data_sp, CRS("+proj=longlat +datum=WGS84"))

writeOGR(data_ll["city"], "/path/to/test.kml", driver = "KML", layer = "city")

结果适用于仅查看位置，但我想更改<styleUrl>属性以及填充<name>属性。没有它，Google地球会显示[no name]属性的位置：

以下是生成的.kml文件：

<?xml version="1.0" encoding="utf-8" ?>
<kml xmlns="http://www.opengis.net/kml/2.2">
<Document><Folder><name>city</name>
  <Placemark>
    <ExtendedData><SchemaData schemaUrl="#city">
        <SimpleData name="city">Saint Paul</SimpleData>
    </SchemaData></ExtendedData>
      <Point><coordinates>-93.001753817020003,44.96282130428127</coordinates></Point>
  </Placemark>
</Folder>
<Schema name="city" id="city">
    <SimpleField name="city" type="string"></SimpleField>
</Schema>
</Document></kml>

我需要获取<name>元素以填充SimpleField name="city"内容，或者为每个<name>City</name>添加<Placemark>个标记。我想要的是最终结果（注释添加了<Style>定义，<styleUrl>属性<Placemark>和添加了<name>属性：

<?xml version="1.0" encoding="utf-8" ?>
<kml xmlns="http://www.opengis.net/kml/2.2">
<Document>

<Style id="custom">
  <IconStyle>
    <scale>1.5</scale>
    <Icon>
      <href>http://upload.wikimedia.org/wikipedia/commons/a/af/Tux.png</href>
    </Icon>
  </IconStyle>
</Style>

<Folder><name>city</name>
  <Placemark>
    <name>Saint Paul</name>
    <styleUrl>#custom</styleUrl>
    <ExtendedData><SchemaData schemaUrl="#city">
        <SimpleData name="city">Saint Paul</SimpleData>
    </SchemaData></ExtendedData>
      <Point><coordinates>-93.001753817020003,44.96282130428127</coordinates></Point>
  </Placemark>
</Folder>
<Schema name="city" id="city">
    <SimpleField name="city" type="string"></SimpleField>
</Schema>
</Document></kml>

这是结果的样子（类似于我的目标）：

rgdal documentation提到了layer_options属性，但没有任何直觉可以解释我......

• layer_options = c("<name>????</name>")？
• layer_options = c("<styleUrl>#custom</styleUrl")？
• 别的什么？

以上尝试直接传递标记似乎不会影响输出。

除了创建writeOGR()的默认输出之外，我在谷歌搜索中找到的示例并不多，如上所示。感谢您的任何建议。

Answer 1

为了扩展@ jlhoward上面的答案，我能够使用kmlPoints()来完成我想要的事情：

data <- data.frame(country = "USA", city = "Saint Paul",
                   lat = 44.9629, lon = -93.00146)

# you may need to install gdal itself for the package to install successfully
# install.packages("rgdal")
library(rgdal)
library(maptools)

data_sp <- data
coordinates(data_sp) <- c("lon", "lat")
proj4string(data_sp) <- CRS("+init=epsg:4238")
data_ll <- spTransform(data_sp, CRS("+proj=longlat +datum=WGS84"))

kmlPoints(data_ll["city"], kmlfile = "~/Desktop/test.kml",
          name = data_ll$city,
          icon = "http://upload.wikimedia.org/wikipedia/commons/a/af/Tux.png")

输出包含所需的<name>属性以及自定义图标的<Style>定义，该定义已成功应用于<Placemark>条目：

readLines("test.kml")

 readLines("test.kml")
 [1] "<?xml version=\"1.0\" encoding=\"UTF-8\"?>"                                   
 [2] "<kml xmlns=\"http://earth.google.com/kml/2.2\">"                              
 [3] "<Document>"                                                                   
 [4] "<name></name>"                                                                
 [5] "<description><![CDATA[]]></description>"                                      
 [6] ""                                                                             
 [7] "<Style id=\"style1\">"                                                        
 [8] "  <IconStyle>"                                                                
 [9] "    <Icon>"                                                                   
[10] "      <href>http://upload.wikimedia.org/wikipedia/commons/a/af/Tux.png</href>"
[11] "    </Icon>"                                                                  
[12] "  </IconStyle>"                                                               
[13] "</Style>"                                                                     
[14] ""                                                                             
[15] "<Placemark>"                                                                  
[16] "  <name>Saint Paul</name>"                                                    
[17] "  <description><![CDATA[]]></description>"                                    
[18] "  <styleUrl>#style1</styleUrl>"                                               
[19] "  <Point>"                                                                    
[20] "    <coordinates>"                                                            
[21] "-93.00175381702,44.9628213042813"                                             
[22] "    </coordinates>"                                                           
[23] "  </Point>"                                                                   
[24] "</Placemark>"                                                                 
[25] "</Document>"                                                                  
[26] "</kml>"  

结果：

Answer 2

好吧，如果你要做的就是填充每个<name>中的<Placemark>元素，这样就可以了：

library(maptools)
kmlPoints(data_ll,"test.kml",name=data$city)
readLines("test.kml")
#  [1] "<?xml version=\"1.0\" encoding=\"UTF-8\"?>"                              
#  [2] "<kml xmlns=\"http://earth.google.com/kml/2.2\">"                         
#  [3] "<Document>"                                                              
#  [4] "<name></name>"                                                           
#  ...
# [15] "<Placemark>"                                                             
# [16] "  <name>Saint Paul</name>"                                               
# [17] "  <description><![CDATA[]]></description>"                               
# [18] "  <styleUrl>#style1</styleUrl>"                                          
# [19] "  <Point>"                                                               
# [20] "    <coordinates>"                                                       
# [21] "-93.00175381702,44.9628213042813"                                        
# [22] "    </coordinates>"                                                      
# [23] "  </Point>"                                                              
# [24] "</Placemark>"                                                            
# [25] "</Document>"                                                             
# [26] "</kml>"                                                                  

如果您还需要更改<Style>，那么我担心您可能不得不使用XML包破解kml文件。