Question

我在R中执行point in Polygon操作。基本上我在这里关注此示例：https://cran.r-project.org/web/packages/sp/vignettes/over.pdf

r1 = cbind(c(180114, 180553, 181127, 181477, 181294, 181007, 180409, 
                 180162, 180114), 
               c(332349, 332057, 332342, 333250, 333558, 333676, 332618, 332413, 332349)
    )
r2 = cbind(c(180042, 180545, 180553, 180314, 179955, 179142, 179437, 
                 179524, 179979, 180042), 
               c(332373, 332026, 331426, 330889, 330683, 331133, 331623, 332152, 332357, 332373)
    )
r3 = cbind(c(179110, 179907, 180433, 180712, 180752, 180329, 179875, 179668, 179572, 179269, 178879, 178600, 178544, 179046, 179110),
               c(331086, 330620, 330494, 330265, 330075, 330233, 330336, 330004, 329783, 329665, 329720, 329933, 330478, 331062, 331086)
    )
r4 = cbind(c(180304, 180403,179632,179420,180304),
               c(332791, 333204, 333635, 333058, 332791)
    )


# dummy Polygons from points
# first: Create Polygon and then Polygons object
# for Polygons object and ID is needed!
sr1 = Polygons(list(Polygon(r1)),"r1")
sr2 = Polygons(list(Polygon(r2)),"r2")
sr3 = Polygons(list(Polygon(r3)),"r3")
sr4 = Polygons(list(Polygon(r4)),"r4")

sr = SpatialPolygons(list(sr1,sr2,sr3,sr4))

plot(sr)


# dummy data, native to R
data(meuse)

# assign coordinates to data
coordinates(meuse) = ~x + y
plot(meuse)

pointsOfInterest <- over(sr, meuse)

这给了我我想要的输出，但是：我正在失去点的lng和lat坐标...当我执行coordinates(meuse) = ~x + y而我执行{{{}}时会发生这种情况1}}之前和之后的数据，str和x的列都消失了。

Answer 1

替代配方，

coordinates(meuse) = meuse[,c("x", "y")]

不会将它们从@data插槽中移除，并导致更大的对象，因为现在重复了坐标。如果你喜欢的话可以使用它;无论如何as.data.frame(meuse)都会放回坐标。

Answer 2

给出

class(meuse)
# [1] "SpatialPointsDataFrame"
# attr(,"package")
# [1] "sp"
class(sr)
# [1] "SpatialPolygons"
# attr(,"package")
# [1] "sp"

以及?over的帮助说：

x =＆＃34; SpatialPolygons＆＃34;，y =＆＃34; SpatialPoints＆＃34;返回多边形索引 y中的点数;如果x是SpatialPolygonsDataFrame，则是data.frame 返回x中与y对应的行。

你可以做到

(idx <- over(sr, as(meuse, "SpatialPoints")) )
# r1 r2 r3 r4 
#  1 44 70 NA 
meuse[na.omit(as.character(idx)), ]
#         coordinates cadmium copper lead zinc  elev       dist   om ffreq soil lime landuse dist.m
# 1  (181072, 333611)    11.7     85  299 1022 7.909 0.00135803 13.6     1    1    1      Ah     50
# 44 (180451, 332175)     1.7     22   65  176 8.694 0.21184300   NA     1    2    0       W    260
# 70 (179474, 331304)     1.8     25   81  241 7.932 0.12481000  2.9     2    2    1      Ah    160

然而，也许你想要像

这样的东西

idx <- apply(rgeos::gIntersects(sr, meuse, T), 2, which)
lapply(idx, function(x) meuse[x, ])

经过sp R后协调

2 个答案: