问题
Is it only me who have the problem with extracting coordinates of a polygon from SpatialPolygonsDataFrame object? I am able to extract other slots of the object (ID,plotOrder) but not coordinates (coords). I don't know what I am doing wrong. Please find below my R session where bdryData being the SpatialPolygonsDataFrame object with two polygons.
> bdryData
An object of class "SpatialPolygonsDataFrame"
Slot "data":
ID GRIDCODE
0 1 0
1 2 0
Slot "polygons":
[[1]]
An object of class "Polygons"
Slot "Polygons":
[[1]]
An object of class "Polygon"
Slot "labpt":
[1] 415499.1 432781.7
Slot "area":
[1] 0.6846572
Slot "hole":
[1] FALSE
Slot "ringDir":
[1] 1
Slot "coords":
[,1] [,2]
[1,] 415499.6 432781.2
[2,] 415498.4 432781.5
[3,] 415499.3 432782.4
[4,] 415499.6 432781.2
Slot "plotOrder":
[1] 1
Slot "labpt":
[1] 415499.1 432781.7
Slot "ID":
[1] "0"
Slot "area":
[1] 0.6846572
[[2]]
An object of class "Polygons"
Slot "Polygons":
[[1]]
An object of class "Polygon"
Slot "labpt":
[1] 415587.3 432779.4
Slot "area":
[1] 20712.98
Slot "hole":
[1] FALSE
Slot "ringDir":
[1] 1
Slot "coords":
[,1] [,2]
[1,] 415499.6 432781.2
[2,] 415505.0 432781.8
[3,] 415506.5 432792.6
[4,] 415508.9 432792.8
[5,] 415515.0 432791.5
[6,] 415517.7 432795.6
[7,] 415528.6 432797.7
[8,] 415538.8 432804.2
[9,] 415543.2 432805.8
[10,] 415545.1 432803.6
[11,] 415547.1 432804.7
[12,] 415551.7 432805.8
[13,] 415557.5 432812.3
[14,] 415564.2 432817.1
[15,] 415568.5 432823.9
[16,] 415571.0 432826.8
[17,] 415573.2 432828.7
[18,] 415574.1 432829.7
[19,] 415576.2 432830.7
[20,] 415580.2 432833.8
[21,] 415589.6 432836.0
[22,] 415593.1 432841.0
[23,] 415592.2 432843.7
[24,] 415590.6 432846.6
[25,] 415589.0 432853.3
[26,] 415584.8 432855.3
[27,] 415579.7 432859.8
[28,] 415577.7 432866.2
[29,] 415575.6 432868.1
[30,] 415566.7 432880.7
[31,] 415562.7 432887.5
[32,] 415559.2 432889.1
[33,] 415561.5 432890.7
[34,] 415586.2 432889.7
[35,] 415587.1 432888.6
[36,] 415588.5 432890.2
[37,] 415598.2 432888.7
[38,] 415599.1 432887.7
[39,] 415601.2 432886.7
[40,] 415603.1 432885.7
[41,] 415605.2 432884.7
[42,] 415606.1 432882.7
[43,] 415607.2 432880.7
[44,] 415608.3 432878.3
[45,] 415612.2 432874.8
[46,] 415614.7 432871.9
[47,] 415617.1 432870.7
[48,] 415622.4 432868.2
[49,] 415622.0 432862.4
[50,] 415624.2 432855.4
[51,] 415633.2 432845.3
[52,] 415639.0 432841.1
[53,] 415642.8 432832.9
[54,] 415647.5 432828.7
[55,] 415654.3 432820.3
[56,] 415654.1 432816.5
[57,] 415658.2 432812.8
[58,] 415661.9 432808.6
[59,] 415663.5 432808.7
[60,] 415668.1 432803.5
[61,] 415676.5 432801.3
[62,] 415679.1 432802.7
[63,] 415680.1 432802.7
[64,] 415681.1 432802.7
[65,] 415682.2 432802.7
[66,] 415685.8 432804.7
[67,] 415691.8 432802.2
[68,] 415693.6 432798.9
[69,] 415696.2 432777.0
[70,] 415689.8 432773.5
[71,] 415683.7 432771.6
[72,] 415680.2 432766.7
[73,] 415679.0 432765.6
[74,] 415676.8 432753.7
[75,] 415671.4 432747.7
[76,] 415662.7 432747.2
[77,] 415658.7 432750.0
[78,] 415657.0 432746.3
[79,] 415654.1 432743.7
[80,] 415652.3 432739.8
[81,] 415649.6 432739.6
[82,] 415648.0 432739.7
[83,] 415641.9 432736.4
[84,] 415633.4 432736.9
[85,] 415630.2 432734.7
[86,] 415622.3 432733.6
[87,] 415614.4 432726.5
[88,] 415617.1 432719.1
[89,] 415612.5 432718.1
[90,] 415610.0 432720.9
[91,] 415606.2 432716.6
[92,] 415603.2 432713.9
[93,] 415601.4 432710.0
[94,] 415580.3 432708.7
[95,] 415545.1 432709.7
[96,] 415543.5 432711.5
[97,] 415534.0 432715.7
[98,] 415527.1 432713.7
[99,] 415521.1 432711.6
[100,] 415505.6 432710.6
[101,] 415501.3 432710.9
[102,] 415499.3 432708.7
[103,] 415495.6 432711.6
[104,] 415482.6 432726.2
[105,] 415477.2 432734.0
[106,] 415478.1 432737.7
[107,] 415479.2 432739.7
[108,] 415480.9 432743.4
[109,] 415486.5 432751.2
[110,] 415493.2 432760.7
[111,] 415494.1 432762.7
[112,] 415498.1 432767.9
[113,] 415497.2 432770.7
[114,] 415490.6 432773.2
[115,] 415493.2 432775.6
[116,] 415496.0 432778.7
[117,] 415499.2 432779.7
[118,] 415499.6 432781.2
Slot "plotOrder":
[1] 1
Slot "labpt":
[1] 415587.3 432779.4
Slot "ID":
[1] "1"
Slot "area":
[1] 20712.98
Slot "plotOrder":
[1] 2 1
Slot "bbox":
min max
x 415477.2 415696.2
y 432708.7 432890.7
Slot "proj4string":
CRS arguments:
+proj=tmerc +lat_0=49 +lon_0=-2 +k=0.9996012717 +x_0=400000 +y_0=-100000
+datum=OSGB36 +units=m +no_defs +ellps=airy
+towgs84=446.448,-125.157,542.060,0.1502,0.2470,0.8421,-20.4894
Subsetting second polygon from bdryData
> bdryData@polygons[[2]]
An object of class "Polygons"
Slot "Polygons":
[[1]]
An object of class "Polygon"
Slot "labpt":
[1] 415587.3 432779.4
Slot "area":
[1] 20712.98
Slot "hole":
[1] FALSE
Slot "ringDir":
[1] 1
Slot "coords":
[,1] [,2]
[1,] 415499.6 432781.2
[2,] 415505.0 432781.8
[3,] 415506.5 432792.6
[4,] 415508.9 432792.8
[5,] 415515.0 432791.5
[6,] 415517.7 432795.6
[7,] 415528.6 432797.7
[8,] 415538.8 432804.2
[9,] 415543.2 432805.8
[10,] 415545.1 432803.6
[11,] 415547.1 432804.7
[12,] 415551.7 432805.8
[13,] 415557.5 432812.3
[14,] 415564.2 432817.1
[15,] 415568.5 432823.9
[16,] 415571.0 432826.8
[17,] 415573.2 432828.7
[18,] 415574.1 432829.7
[19,] 415576.2 432830.7
[20,] 415580.2 432833.8
[21,] 415589.6 432836.0
[22,] 415593.1 432841.0
[23,] 415592.2 432843.7
[24,] 415590.6 432846.6
[25,] 415589.0 432853.3
[26,] 415584.8 432855.3
[27,] 415579.7 432859.8
[28,] 415577.7 432866.2
[29,] 415575.6 432868.1
[30,] 415566.7 432880.7
[31,] 415562.7 432887.5
[32,] 415559.2 432889.1
[33,] 415561.5 432890.7
[34,] 415586.2 432889.7
[35,] 415587.1 432888.6
[36,] 415588.5 432890.2
[37,] 415598.2 432888.7
[38,] 415599.1 432887.7
[39,] 415601.2 432886.7
[40,] 415603.1 432885.7
[41,] 415605.2 432884.7
[42,] 415606.1 432882.7
[43,] 415607.2 432880.7
[44,] 415608.3 432878.3
[45,] 415612.2 432874.8
[46,] 415614.7 432871.9
[47,] 415617.1 432870.7
[48,] 415622.4 432868.2
[49,] 415622.0 432862.4
[50,] 415624.2 432855.4
[51,] 415633.2 432845.3
[52,] 415639.0 432841.1
[53,] 415642.8 432832.9
[54,] 415647.5 432828.7
[55,] 415654.3 432820.3
[56,] 415654.1 432816.5
[57,] 415658.2 432812.8
[58,] 415661.9 432808.6
[59,] 415663.5 432808.7
[60,] 415668.1 432803.5
[61,] 415676.5 432801.3
[62,] 415679.1 432802.7
[63,] 415680.1 432802.7
[64,] 415681.1 432802.7
[65,] 415682.2 432802.7
[66,] 415685.8 432804.7
[67,] 415691.8 432802.2
[68,] 415693.6 432798.9
[69,] 415696.2 432777.0
[70,] 415689.8 432773.5
[71,] 415683.7 432771.6
[72,] 415680.2 432766.7
[73,] 415679.0 432765.6
[74,] 415676.8 432753.7
[75,] 415671.4 432747.7
[76,] 415662.7 432747.2
[77,] 415658.7 432750.0
[78,] 415657.0 432746.3
[79,] 415654.1 432743.7
[80,] 415652.3 432739.8
[81,] 415649.6 432739.6
[82,] 415648.0 432739.7
[83,] 415641.9 432736.4
[84,] 415633.4 432736.9
[85,] 415630.2 432734.7
[86,] 415622.3 432733.6
[87,] 415614.4 432726.5
[88,] 415617.1 432719.1
[89,] 415612.5 432718.1
[90,] 415610.0 432720.9
[91,] 415606.2 432716.6
[92,] 415603.2 432713.9
[93,] 415601.4 432710.0
[94,] 415580.3 432708.7
[95,] 415545.1 432709.7
[96,] 415543.5 432711.5
[97,] 415534.0 432715.7
[98,] 415527.1 432713.7
[99,] 415521.1 432711.6
[100,] 415505.6 432710.6
[101,] 415501.3 432710.9
[102,] 415499.3 432708.7
[103,] 415495.6 432711.6
[104,] 415482.6 432726.2
[105,] 415477.2 432734.0
[106,] 415478.1 432737.7
[107,] 415479.2 432739.7
[108,] 415480.9 432743.4
[109,] 415486.5 432751.2
[110,] 415493.2 432760.7
[111,] 415494.1 432762.7
[112,] 415498.1 432767.9
[113,] 415497.2 432770.7
[114,] 415490.6 432773.2
[115,] 415493.2 432775.6
[116,] 415496.0 432778.7
[117,] 415499.2 432779.7
[118,] 415499.6 432781.2
Slot "plotOrder":
[1] 1
Slot "labpt":
[1] 415587.3 432779.4
Slot "ID":
[1] "1"
Slot "area":
[1] 20712.98
Extracting slots
> bdryData@polygons[[2]]@ID
[1] "1"
> bdryData@polygons[[2]]@plotOrder
[1] 1
But problem with coordinates
> bdryData@polygons[[2]]@coords
Error: no slot of name "coords" for this object of class "Polygons"
Any help is really appreciated. Thanks.
回答1:
Finally, I figured out that I didn't parse the output correctly. The correct way to do is bdryData@polygons[[2]]@Polygons[[1]]@coords. Mind the difference in command polygons(Polygons and polygons) and it took me ages to find out.
回答2:
This took me a while to figure out too. The following function I wrote worked for me. sp.df should be SpatialPolygonsDataFrame.
extractCoords <- function(sp.df)
{
results <- list()
for(i in 1:length(sp.df@polygons[[1]]@Polygons))
{
results[[i]] <- sp.df@polygons[[1]]@Polygons[[i]]@coords
}
results <- Reduce(rbind, results)
results
}
回答3:
Use the coordinates() function from the sp package. It should give you the values in a list format.
You can also get the Polygon attribute from the shapefile.
mfile = readOGR(dsn=dsn,layer=layername)
polys = attr(mfile,'polygons')
npolys = length(polys)
for (i in 1:npolys){
poly = polys[[i]]
polys2 = attr(poly,'Polygons')
npolys2 = length(polys2)
for (j in 1:npolys2){
#do stuff with these values
coords = coordinates(polys2[[j]])
}
}
回答4:
This question was also addressed on gis.stackexchange, here. I made an example below testing all the options mentioned here by @mdsumner. Also have a look here
library(sp)
library(sf)
#> Warning: package 'sf' was built under R version 3.5.3
#> Linking to GEOS 3.6.1, GDAL 2.2.3, PROJ 4.9.3
library(raster)
library(spbabel)
#> Warning: package 'spbabel' was built under R version 3.5.3
library(tmap)
library(microbenchmark)
library(ggplot2)
# Prepare data
data(World)
# Convert from sf to sp objects
atf_sf <- World[World$iso_a3 == "ATF", ]
atf_sp <- as(atf_sf, "Spatial")
atf_sp
#> class : SpatialPolygonsDataFrame
#> features : 1
#> extent : 5490427, 5660887, -6048972, -5932855 (xmin, xmax, ymin, ymax)
#> coord. ref. : +proj=eck4 +lon_0=0 +x_0=0 +y_0=0 +datum=WGS84 +units=m +no_defs +ellps=WGS84 +towgs84=0,0,0
#> variables : 15
#> # A tibble: 1 x 15
#> iso_a3 name sovereignt continent area pop_est pop_est_dens economy
#> <fct> <fct> <fct> <fct> <S3:> <dbl> <dbl> <fct>
#> 1 ATF Fr. ~ France Seven se~ 7257~ 140 0.0193 6. Dev~
#> # ... with 7 more variables: income_grp <fct>, gdp_cap_est <dbl>,
#> # life_exp <dbl>, well_being <dbl>, footprint <dbl>, inequality <dbl>,
#> # HPI <dbl>
# Try various functions:
raster::geom(atf_sp)
#> object part cump hole x y
#> [1,] 1 1 1 0 5550200 -5932855
#> [2,] 1 1 1 0 5589907 -5964836
#> [3,] 1 1 1 0 5660887 -5977490
#> [4,] 1 1 1 0 5656160 -5996685
#> [5,] 1 1 1 0 5615621 -6042456
#> [6,] 1 1 1 0 5490427 -6048972
#> [7,] 1 1 1 0 5509148 -5995424
#> [8,] 1 1 1 0 5536900 -5953683
#> [9,] 1 1 1 0 5550200 -5932855
ggplot2::fortify(atf_sp)
#> Regions defined for each Polygons
#> long lat order hole piece id group
#> 1 5550200 -5932855 1 FALSE 1 8 8.1
#> 2 5589907 -5964836 2 FALSE 1 8 8.1
#> 3 5660887 -5977490 3 FALSE 1 8 8.1
#> 4 5656160 -5996685 4 FALSE 1 8 8.1
#> 5 5615621 -6042456 5 FALSE 1 8 8.1
#> 6 5490427 -6048972 6 FALSE 1 8 8.1
#> 7 5509148 -5995424 7 FALSE 1 8 8.1
#> 8 5536900 -5953683 8 FALSE 1 8 8.1
#> 9 5550200 -5932855 9 FALSE 1 8 8.1
spbabel::sptable(atf_sp)
#> # A tibble: 9 x 6
#> object_ branch_ island_ order_ x_ y_
#> <int> <int> <lgl> <int> <dbl> <dbl>
#> 1 1 1 TRUE 1 5550200. -5932855.
#> 2 1 1 TRUE 2 5589907. -5964836.
#> 3 1 1 TRUE 3 5660887. -5977490.
#> 4 1 1 TRUE 4 5656160. -5996685.
#> 5 1 1 TRUE 5 5615621. -6042456.
#> 6 1 1 TRUE 6 5490427. -6048972.
#> 7 1 1 TRUE 7 5509148. -5995424.
#> 8 1 1 TRUE 8 5536900. -5953683.
#> 9 1 1 TRUE 9 5550200. -5932855.
as.data.frame(as(as(atf_sp, "SpatialLinesDataFrame"),"SpatialPointsDataFrame"))
#> iso_a3 name sovereignt continent
#> 8 ATF Fr. S. Antarctic Lands France Seven seas (open ocean)
#> 8.1 ATF Fr. S. Antarctic Lands France Seven seas (open ocean)
#> 8.2 ATF Fr. S. Antarctic Lands France Seven seas (open ocean)
#> 8.3 ATF Fr. S. Antarctic Lands France Seven seas (open ocean)
#> 8.4 ATF Fr. S. Antarctic Lands France Seven seas (open ocean)
#> 8.5 ATF Fr. S. Antarctic Lands France Seven seas (open ocean)
#> 8.6 ATF Fr. S. Antarctic Lands France Seven seas (open ocean)
#> 8.7 ATF Fr. S. Antarctic Lands France Seven seas (open ocean)
#> 8.8 ATF Fr. S. Antarctic Lands France Seven seas (open ocean)
#> area pop_est pop_est_dens economy
#> 8 7257.455 [km^2] 140 0.01929051 6. Developing region
#> 8.1 7257.455 [km^2] 140 0.01929051 6. Developing region
#> 8.2 7257.455 [km^2] 140 0.01929051 6. Developing region
#> 8.3 7257.455 [km^2] 140 0.01929051 6. Developing region
#> 8.4 7257.455 [km^2] 140 0.01929051 6. Developing region
#> 8.5 7257.455 [km^2] 140 0.01929051 6. Developing region
#> 8.6 7257.455 [km^2] 140 0.01929051 6. Developing region
#> 8.7 7257.455 [km^2] 140 0.01929051 6. Developing region
#> 8.8 7257.455 [km^2] 140 0.01929051 6. Developing region
#> income_grp gdp_cap_est life_exp well_being footprint
#> 8 2. High income: nonOECD 114285.7 NA NA NA
#> 8.1 2. High income: nonOECD 114285.7 NA NA NA
#> 8.2 2. High income: nonOECD 114285.7 NA NA NA
#> 8.3 2. High income: nonOECD 114285.7 NA NA NA
#> 8.4 2. High income: nonOECD 114285.7 NA NA NA
#> 8.5 2. High income: nonOECD 114285.7 NA NA NA
#> 8.6 2. High income: nonOECD 114285.7 NA NA NA
#> 8.7 2. High income: nonOECD 114285.7 NA NA NA
#> 8.8 2. High income: nonOECD 114285.7 NA NA NA
#> inequality HPI Lines.NR Lines.ID Line.NR coords.x1 coords.x2
#> 8 NA NA 1 8 1 5550200 -5932855
#> 8.1 NA NA 1 8 1 5589907 -5964836
#> 8.2 NA NA 1 8 1 5660887 -5977490
#> 8.3 NA NA 1 8 1 5656160 -5996685
#> 8.4 NA NA 1 8 1 5615621 -6042456
#> 8.5 NA NA 1 8 1 5490427 -6048972
#> 8.6 NA NA 1 8 1 5509148 -5995424
#> 8.7 NA NA 1 8 1 5536900 -5953683
#> 8.8 NA NA 1 8 1 5550200 -5932855
# What about speed? raster::geom is the fastest
res <- microbenchmark(raster::geom(atf_sp),
ggplot2::fortify(atf_sp),
spbabel::sptable(atf_sp),
as.data.frame(as(as(atf_sp, "SpatialLinesDataFrame"),
"SpatialPointsDataFrame")))
ggplot2::autoplot(res)
#> Coordinate system already present. Adding new coordinate system, which will replace the existing one.
Created on 2019-03-23 by the reprex package (v0.2.1)
回答5:
ggplot2's fortify() function may be deprecated at some point so the broom package is now suggested
library(broom)
broom::tidy(atf_sp)
来源：https://stackoverflow.com/questions/29803253/r-extracting-coordinates-from-spatialpolygonsdataframe