Question

通常情况下，您可以使用可靠的readOGR将geojson文件读入R中，如图here所示。

然而，这对于多功能地理学来说是失败的。

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，我不知道怎么做。

非常欢迎任何想法。

令人惊奇的事情：GitHub displays the data natively on the browser，而R甚至不能（看似）阅读它！

解决方案的替代方法：

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

Answer 1

您可以将require_geomType参数用于各种GDAL函数，以提取您需要的功能：

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")

enter image description here

Answer 2

你可以在命令行中使用ogr2ogr将这个怪异的嵌合体分成合理的东西：

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

并且类似于点和多边形。

几年前有一些关于将OGR_SQL实现到readOGR的喋喋不休，此时你可以从R做到这一点，但罗杰不想这样做，没有人想要帮助：（

创建拆分geojson文件后，您可以将它们读入单个rgeos::SpatialCollections对象：

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)

如果你想尝试使用geojsonio，那么你可以使用Filter从几何集合中选择给定几何的列表元素

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

但是你仍然需要构建一些你可以进入单独的R实体的东西......

Answer 3

几年后，有两种选择-library(geojsonsf)和library(sf)都将读取geojson并转换为sf个对象

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 )

让我们看看

library(mapdeck)

set_token( "MAPBOX_TOKEN" )

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

将“多特征”GeoJSON的特征转换为R空间对象

3 个答案: