将sf多边形转换为sp

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英文:

converting sf multipolygon to sp

问题

我有一个包含多边形的sf对象，我需要将其转换为sp对象。似乎使用sf转换函数无法正常工作。

我尝试过以下方法：

  1. library(absmapsdata)
  2. library(sp)
  3. library(sf)
  5. vic_sa4 <- sa42021
  7. class(vic_sa4)
  9. vic_sa4_sp <- as_Spatial(vic_sa4)
  11. tmp <- as(vic_sa4, 'Spatial')
  13. vic_sa4_sp <- sf:::as_Spatial(st_geometry(vic_sa4))
  15. as(vic_sa4, "Spatial")

但是都给我返回了这个错误 - 但几何图形确实存在！如何解决这个问题？

  1. 在选择函数 'addAttrToGeom' 的方法时评估参数 'x' 时出错：sp类不支持空几何图形
英文:

I have sf object with multipolygons which i need to convert to sp object. It does not seem to work with sf conversion functions.

I tried

  1. library(absmapsdata)
  2. library(sp)
  3. library(sf)
  5. vic_sa4&lt;-sa42021
  7. class(vic_sa4)
  9. vic_sa4_sp &lt;- as_Spatial(vic_sa4)
  11. tmp &lt;-as(vic_sa4, &#39;Spatial&#39;)
  13. vic_sa4_sp &lt;- sf:::as_Spatial(st_geometry(vic_sa4))
  15. as(vic_sa4, &quot;Spatial&quot;)

it all gives me this error - but the geometry is indeed there! how to fix this?

  1. error in evaluating the argument &#39;x&#39; in selecting a method for function &#39;addAttrToGeom&#39;: empty geometries are not supported by sp classes

答案1

得分: 2

需要删除具有空几何形状的项目。您可以使用 st_is_empty 进行测试。这里有一些由过多的负缓冲导致的空几何形状示例：

  1. p = st_point(c(1,1))
  2. pv = st_sfc(p,p,p,p,p)
  3. bv = st_buffer(pv, c(1,1,0,-1,2))
  4. d = st_sf(bv)

测试：

  1. > st_is_empty(d)
  2. [1] FALSE FALSE  TRUE  TRUE FALSE

删除：

  1. dnonempty = d[!st_is_empty(d),]

转换：

  1. > library(sp) ; library(raster) # raster的漂亮sp打印方法
  3. > as(dnonempty, "Spatial")
  4. class       : SpatialPolygonsDataFrame 
  5. features    : 3 
  6. extent      : -1, 3, -1, 3  (xmin, xmax, ymin, ymax)
  7. crs         : NA 
  8. variables   : 0
英文:

You need to get rid of the items with empty geometry. You can test with st_is_empty. Here's a thing with some empty geometries caused by excessive negative buffering into nothingness:

  1. p = st_point(c(1,1))
  2. pv = st_sfc(p,p,p,p,p)
  3. bv = st_buffer(pv, c(1,1,0,-1,2))
  4. d = st_sf(bv)
  6. &gt; d
  7. Simple feature collection with 5 features and 0 fields (with 2 geometries empty)
  8. Geometry type: POLYGON
  9. Dimension:     XY
  10. Bounding box:  xmin: -1 ymin: -1 xmax: 3 ymax: 3
  11. CRS:           NA
  12.                               bv
  13. 1 POLYGON ((2 1, 1.99863 0.94...
  14. 2 POLYGON ((2 1, 1.99863 0.94...
  15. 3                  POLYGON EMPTY
  16. 4                  POLYGON EMPTY
  17. 5 POLYGON ((3 1, 2.997259 0.8...

Test:

  1. &gt; st_is_empty(d)
  2. [1] FALSE FALSE  TRUE  TRUE FALSE

Remove:

  1. dnonempty = d[!st_is_empty(d),]

Convert:

  1. &gt; library(sp) ; library(raster) # raster&#39;s nice sp print method
  3. &gt; as(d, &quot;Spatial&quot;)
  4. Error in h(simpleError(msg, call)) : 
  5.   error in evaluating the argument &#39;x&#39; in selecting a method for function &#39;addAttrToGeom&#39;: empty geometries are not supported by sp classes: conversion failed
  7. &gt; as(dnonempty, &quot;Spatial&quot;)
  8. class       : SpatialPolygonsDataFrame 
  9. features    : 3 
  10. extent      : -1, 3, -1, 3  (xmin, xmax, ymin, ymax)
  11. crs         : NA 
  12. variables   : 0

huangapple
  • 本文由 发表于 2023年6月19日 13:42:25
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  • r
  • r-sf
  • r-sp
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