将"多特征"GeoJSON的特征转换为R空间对象

Question

通常情况下,你可以阅读GeoJSON的文件成R与信赖readOGR,如图所示这里.

但是,对于多功能地理数据而言,这是失败的.

可重复的例子:

downloader::download("https://github.com/Robinlovelace/Creating-maps-in-R/raw/master/data/test-multifeature.geojson", "test.geojson")
test <- rgdal::readOGR("test.geojson", "OGRGeoJSON") # fails with:

Error in ogrInfo(dsn = dsn, layer = layer, encoding = encoding, use_iconv = use_iconv,  : 
  Multiple incompatible geometries: wkbPoint: 98; wkbLineString: 660; wkbPolygon: 23

错误消息足够清晰并指示解决方案:拆分功能.除了用正则表达式做这个,我不知道怎么样.

任何想法都非常受欢迎.

令人惊奇的是:GitHub在浏览器上本地显示数据,而R甚至不能(看似)读取它!

解决方案的替代方法:

test <- geojsonio::geojson_read("test.geojson")

Answer 1

您可以使用require_geomType各种GDAL函数的参数来提取所需的功能:

library(rgdal)

ogrListLayers("test.geojson")
## [1] "OGRGeoJSON"
## attr(,"driver")
## [1] "GeoJSON"
## attr(,"nlayers")
## [1] 1

# This fails but you can at least see the geoms it whines about
ogrInfo("test.geojson", "OGRGeoJSON")
## Error in ogrInfo("test.geojson", "OGRGeoJSON") : 
##   Multiple incompatible geometries: wkbPoint: 98; wkbLineString: 660; wkbPolygon: 23


ogrInfo("test.geojson", "OGRGeoJSON", require_geomType="wkbPoint")
## NOTE: keeping only 98 wkbPoint of 781 features
##     note that extent applies to all features
## Source: "test.geojson", layer: "OGRGeoJSON"
## Driver: GeoJSON number of rows 781 
##   selected geometry type: wkbPoint with 98 rows
## Feature type: wkbPoint with 2 dimensions
## Extent: (12.48326 41.88355) - (12.5033 41.89629)
## CRS: +proj=longlat +datum=WGS84 +no_defs  
## Number of fields: 78 
##                        name type length typeName
## 1                      area    4      0   String
## 2                   bicycle    4      0   String
## ...
## LONG LIST - 78 total


ogrInfo("test.geojson", "OGRGeoJSON", require_geomType="wkbLineString")
## NOTE: keeping only 660 wkbLineString of 781 features
##     note that extent applies to all features
## Source: "test.geojson", layer: "OGRGeoJSON"
## Driver: GeoJSON number of rows 781 
##   selected geometry type: wkbLineString with 660 rows
## Feature type: wkbLineString with 2 dimensions
## Extent: (12.48326 41.88355) - (12.5033 41.89629)
## CRS: +proj=longlat +datum=WGS84 +no_defs  
## Number of fields: 78 
##                        name type length typeName
## 1                      area    4      0   String
## 2                   bicycle    4      0   String
## ...
## LONG LIST - 78 total (same as above)


ogrInfo("test.geojson", "OGRGeoJSON", require_geomType="wkbPolygon")
## NOTE: keeping only 23 wkbPolygon of 781 features
##     note that extent applies to all features
## Source: "test.geojson", layer: "OGRGeoJSON"
## Driver: GeoJSON number of rows 781 
##   selected geometry type: wkbPolygon with 23 rows
## Feature type: wkbPolygon with 2 dimensions
## Extent: (12.48326 41.88355) - (12.5033 41.89629)
## CRS: +proj=longlat +datum=WGS84 +no_defs  
## Number of fields: 78 
##                        name type length typeName
## 1                      area    4      0   String
## 2                   bicycle    4      0   String
## ...
## LONG LIST - 78 total (same as above)


points <- readOGR("test.geojson", "OGRGeoJSON", require_geomType="wkbPoint")
## OGR data source with driver: GeoJSON 
## Source: "test.geojson", layer: "OGRGeoJSON"
## with 781 features;
## Selected wkbPoint feature type, with 98 rows
## It has 78 fields
## NOTE: keeping only 98 wkbPoint of 781 features

lines <- readOGR("test.geojson", "OGRGeoJSON", require_geomType="wkbLineString")
## OGR data source with driver: GeoJSON 
## Source: "test.geojson", layer: "OGRGeoJSON"
## with 781 features;
## Selected wkbLineString feature type, with 660 rows
## It has 78 fields
## NOTE: keeping only 660 wkbLineString of 781 features

polygons <- readOGR("test.geojson", "OGRGeoJSON", require_geomType="wkbPolygon")
## OGR data source with driver: GeoJSON 
## Source: "test.geojson", layer: "OGRGeoJSON"
## with 781 features;
## Selected wkbPolygon feature type, with 23 rows
## It has 78 fields
## NOTE: keeping only 23 wkbPolygon of 781 features

# prove they red in things
plot(lines, col="#7f7f7f")
plot(polygons, add=TRUE)
plot(points, add=TRUE, col="red")