R_estrarre le coordinate da SpatialPolygonsDataFrame

Question

Sono solo io che ho il problema di estrarre le coordinate di un poligono dall'oggetto SpatialPolygonsDataFrame? Sono in grado di estrarre gli altri slot dell'oggetto (ID, plotOrder) ma non le coordinate (coords). Non so cosa sto sbagliando. Si prega di trovare sotto la mia sessione R dove bdryData è l'oggetto SpatialPolygonsDataFrame con due poligoni.

> 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 

Impostazione secondaria secondo poligono da 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 

slot Estrazione

> bdryData@polygons[[2]]@ID 
[1] "1" 

> bdryData@polygons[[2]]@plotOrder 
[1] 1 

Ma problema con coordinate

> bdryData@polygons[[2]]@coords 
Error: no slot of name "coords" for this object of class "Polygons" 

Qualsiasi aiuto è molto apprezzato. Grazie.

Answer 1

Infine, ho capito che non ho analizzato correttamente l'output. Il modo corretto per fare è bdryData@polygons[[2]]@Polygons[[1]]@coords. Ricorda la differenza nel comando polygons (Polygons e polygons) e mi ci sono voluti anni per scoprirlo.

Answer 2

Utilizzare la funzione coordinates() dal pacchetto sp. Dovrebbe darti i valori in un formato elenco.

È inoltre possibile ottenere l'attributo Poligono dallo 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]]) 
    } 
} 

Answer 3

Questo mi ci è voluto un po 'per capire anche. La seguente funzione che ho scritto ha funzionato per me. sp.df dovrebbe essere 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 
}