问题描述
我不熟悉地理数据。我已经打开并修改了 SpatialpolygonsDataFrame rnaturalearthdata::countries50。在使用 st_as_sf() 和 st_shift_longitude() 之后，它现在是一个 SpatialPointsDataFrame。与 SpatialPointsDataFrame 附加的数据相比，保存文件的最佳方法是什么，以便我不会丢失任何数据？我阅读了 this 帖子，似乎在地理投影方面存在差异。我担心如果我以一种方式保存它，我会丢失不可恢复的信息（比如当我将数据帧保存到 .csv 而不是 .RData 时，我会丢失 R 对象的名称）。
这是我考虑过的：
library(dplyr) # for pipes
mySPDF <- rnaturalearthdata::countries50 %>%
st_as_sf() %>%
st_shift_longitude()
library(sf)
st_write(mySPDF,"mySPDF.shp") # error
library(maptools)
writeSpatialShape(mySPDF,"mySPDF") # warning: 1: writeSpatialShape is deprecated; use rgdal::writeOGR or sf::st_write
来自上面引用的帖子：
library(rgdal)
writeOGR(obj=mySPDF,dsn="tempdir",layer="mySPDF",driver="ESRI Shapefile") # this is in geographical projection
所以我想知道如何保存/导出我的 SpatialPointsDataFrame 以便我可以在不丢失信息的情况下打开它？
解决方法
只是为了澄清，mySPDF 不是 SpatialPointsDataFrame 而是 sf 对象，因为您使用包含多边形的 st_as_sf 将其转换（因为 mySPDF 是一个SpatialPolygonsDataFrame).
正如您所说，您不熟悉地理数据，我建议您使用 sf 而不是 sp，尽管您可以轻松地在两种数据类型之间进行转换。
我试过这个，它在这个版本上工作，看看它是否符合你的需求：
library(dplyr) # for pipes
#>
#> Attaching package: 'dplyr'
#> The following objects are masked from 'package:stats':
#>
#> filter,lag
#> The following objects are masked from 'package:base':
#>
#> intersect,setdiff,setequal,union
library(sf)
#> Linking to GEOS 3.6.1,GDAL 2.2.3,PROJ 4.9.3
# Getting data - this may be corrupted
mySPDF <- rnaturalearthdata::countries50
class(mySPDF)
#> [1] "SpatialPolygonsDataFrame"
#> attr(,"package")
#> [1] "sp"
# To sf
mySPDF_sf <- mySPDF %>%
st_as_sf() %>%
st_shift_longitude()
#> Warning in CPL_wrap_dateline(x,options,quiet): GDAL Error 1:
#> TopologyException: Input geom 0 is invalid: Self-intersection at or near point
#> 16.123482736917911 -84.347832109632833 at 16.123482736917911 -84.347832109632833
#> Warning in CPL_wrap_dateline(x,quiet): GDAL Error 1:
#> TopologyException: Input geom 0 is invalid: Self-intersection at or near point
#> 16.123482736917911 -84.347832109632833 at 16.123482736917911 -84.347832109632833
# Check object
st_geometry(mySPDF_sf)
#> Geometry set for 241 features
#> geometry type: MULTIPOLYGON
#> dimension: XY
#> bbox: xmin: 5.684342e-14 ymin: -89.99893 xmax: 359.9953 ymax: 83.59961
#> CRS: +proj=longlat +datum=WGS84 +no_defs +ellps=WGS84 +towgs84=0,0
#> First 5 geometries:
#> MULTIPOLYGON (((290.1009 12.452,290.1043 12.42...
#> MULTIPOLYGON (((74.89131 37.23164,74.84023 37....
#> MULTIPOLYGON (((14.19082 -5.875977,14.39863 -5...
#> MULTIPOLYGON (((296.9988 18.22178,296.84 18.17...
#> MULTIPOLYGON (((20.06396 42.54727,20.10352 42....
st_write(mySPDF_sf,"mySPDF.shp") # Some warnings,but may be spurious
#> Writing layer `mySPDF' to data source `mySPDF.shp' using driver `ESRI Shapefile'
#> Writing 241 features with 63 fields and geometry type Multi Polygon.
#> Warning in CPL_write_ogr(obj,dsn,layer,driver,#> as.character(dataset_options),: GDAL Message 1: Value 156050883 of field
#> pop_est of feature 22 not successfully written. Possibly due to too larger
#> number with respect to field width
#> Warning in CPL_write_ogr(obj,: GDAL Message 1: Value 198739269 of field
#> pop_est of feature 32 not successfully written. Possibly due to too larger
#> number with respect to field width
#> Warning in CPL_write_ogr(obj,: GDAL Message 1: Value 1338612970 of field
#> pop_est of feature 41 not successfully written. Possibly due to too larger
#> number with respect to field width
#> Warning in CPL_write_ogr(obj,: GDAL Message 1: Value 240271522 of field
#> pop_est of feature 96 not successfully written. Possibly due to too larger
#> number with respect to field width
#> Warning in CPL_write_ogr(obj,: GDAL Message 1: Value 1166079220 of field
#> pop_est of feature 98 not successfully written. Possibly due to too larger
#> number with respect to field width
#> Warning in CPL_write_ogr(obj,: GDAL Message 1: Value 127078679 of field
#> pop_est of feature 110 not successfully written. Possibly due to too larger
#> number with respect to field width
#> Warning in CPL_write_ogr(obj,: GDAL Message 1: Value 111211789 of field
#> pop_est of feature 139 not successfully written. Possibly due to too larger
#> number with respect to field width
#> Warning in CPL_write_ogr(obj,: GDAL Message 1: Value 149229090 of field
#> pop_est of feature 158 not successfully written. Possibly due to too larger
#> number with respect to field width
#> Warning in CPL_write_ogr(obj,: GDAL Message 1: Value 176242949 of field
#> pop_est of feature 167 not successfully written. Possibly due to too larger
#> number with respect to field width
#> Warning in CPL_write_ogr(obj,: GDAL Message 1: Value 140041247 of field
#> pop_est of feature 183 not successfully written. Possibly due to too larger
#> number with respect to field width
#> Warning in CPL_write_ogr(obj,: GDAL Message 1: Value 313973000 of field
#> pop_est of feature 226 not successfully written. Possibly due to too larger
#> number with respect to field width
# Check if I can reload the shape
st_read("mySPDF.shp")
#> Reading layer `mySPDF' from data source `C:\Users\ xx\AppData\Local\Temp\RtmpCW170K\reprex25781dc712ca\mySPDF.shp' using driver `ESRI Shapefile'
#> Simple feature collection with 241 features and 63 fields
#> geometry type: MULTIPOLYGON
#> dimension: XY
#> bbox: xmin: 5.684342e-14 ymin: -89.99893 xmax: 359.9953 ymax: 83.59961
#> CRS: 4326
sessionInfo()
#> R version 3.6.3 (2020-02-29)
#> Platform: x86_64-w64-mingw32/x64 (64-bit)
#> Running under: Windows 10 x64 (build 18363)
#>
#> Matrix products: default
#>
#> locale:
#> [1] LC_COLLATE=Spanish_Spain.1252 LC_CTYPE=Spanish_Spain.1252
#> [3] LC_MONETARY=Spanish_Spain.1252 LC_NUMERIC=C
#> [5] LC_TIME=Spanish_Spain.1252
#>
#> attached base packages:
#> [1] stats graphics grDevices utils datasets methods base
#>
#> other attached packages:
#> [1] sf_0.9-2 dplyr_1.0.4
#>
#> loaded via a namespace (and not attached):
#> [1] Rcpp_1.0.4.6 knitr_1.31 magrittr_1.5
#> [4] units_0.6-6 tidyselect_1.1.0 lattice_0.20-41
#> [7] R6_2.4.1 rlang_0.4.10 rnaturalearthdata_0.1.0
#> [10] stringr_1.4.0 highr_0.8 tools_3.6.1
#> [13] grid_3.6.1 xfun_0.21 KernSmooth_2.23-16
#> [16] e1071_1.7-3 DBI_1.1.0 class_7.3-16
#> [19] htmltools_0.4.0 ellipsis_0.3.1 assertthat_0.2.1
#> [22] yaml_2.2.1 digest_0.6.25 tibble_3.0.6
#> [25] lifecycle_1.0.0 crayon_1.3.4 purrr_0.3.4
#> [28] vctrs_0.3.6 glue_1.4.0 evaluate_0.14
#> [31] rmarkdown_2.7 sp_1.4-1 stringi_1.4.6
#> [34] compiler_3.6.1 pillar_1.4.3 generics_0.0.2
#> [37] classInt_0.4-3 pkgconfig_2.0.3
由 reprex package (v0.3.0) 于 2021 年 4 月 8 日创建