将“多特征”GeoJSON的特征转换为R空间对象

Question

通常，您可以使用可靠的readOGR将geojson文件读入R中，如此处所示here。

但是，对于多要素的geojson，这种方法会失败。

可重现的示例：

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

错误信息已经很清楚，指出了解决方案：拆分功能。除了使用正则表达式之外，我不知道其他方法。欢迎提供任何想法。令人惊奇的是，GitHub在浏览器上本地显示数据，而R甚至（看起来）无法读取它！另一种解决方案的替代方法：

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

- RobinLovelace

Answer 1

您可以在各种GDAL函数中使用“require_geomType”参数来提取所需的要素：

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")

- hrbrmstr

---

那是最近发布的rgdal吗？我在0.9-1中没有看到它 - 刚刚升级到0.9-3，现在我有了！ - Spacedman

我认为它是在0.9-2版本中加入的。它非常有用，特别是对于这些时髦的GeoJSON形状文件，这些酷孩子们现在正在使用的文件；-) - hrbrmstr

很酷。我的多功能/GeoJSON探索总结与R/gdal可以在这里找到：http://rpubs.com/RobinLovelace/84577。如果您使用Ubuntu，可以更新gdal：$ sudo add-apt-repository ppa:ubuntugis/ubuntugis-unstable && sudo apt-get update $ sudo apt-get install gdal-bin - RobinLovelace

Answer 2

您可以在命令行上使用ogr2ogr将这个庞然大物分割成有意义的部分：

ogr2ogr -where "OGR_GEOMETRY='LINESTRING'" \
     -f "GeoJSON" lines.geojson  test.geojson

同样的，对于点和多边形也是如此。

几年前曾经有些讨论关于将OGR_SQL实现到readOGR中，在那时你就可以从R中实现这个功能，但Roger不想这么做，也没有人愿意帮忙 :(

一旦你创建了拆分后的geojson文件，就可以将它们读入单个rgeos::SpatialCollections对象中：

points=readOGR("points.geojson","OGRGeoJSON")
polys=readOGR("polygons.geojson","OGRGeoJSON")
lines=readOGR("lines.geojson","OGRGeoJSON")
require(rgeos)
g = SpatialCollections(points=points, lines=lines, polygons=polys)
plot(g)

如果您想尝试使用geojsonio，则可以使用过滤器从几何集合中选择给定几何形状的列表元素。

polygon_features = Filter(
    function(f){f$geometry$type=="Polygon"},
    test$features)

但是你仍然需要构建一些可以分离成不同 R 实体的东西...

- Spacedman

Answer 3

几年后，有两个替代方案 - library(geojsonsf) 和 library(sf) 都可以读取geojson并转换为sf对象。

url <- 'https://github.com/Robinlovelace/Creating-maps-in-R/raw/master/data/test-multifeature.geojson'

## these give the same result
sf <- geojsonsf::geojson_sf( url )
sf <- sf::st_read( url )

---

让我们来看看。

library(mapdeck)

set_token( "MAPBOX_TOKEN" )

mapdeck( style = mapdeck_style("light") ) %>%
    add_sf( sf )

- SymbolixAU