识别属于纬度和经度坐标的邮政编码

Question

我在R中有几个数据帧。第一个数据帧包含按市值计算的一组经度和纬度坐标的凸包（由R中的chull提供）。看起来像这样：

MyGeo<- "Part of Chicago & Wisconsin"
Longitude <- c(-90.31914,  -90.61911,  -89.37842,  -88.0988,  -87.44875)
Latitude <- c(38.45781, 38.80097, 43.07961, 43.0624,41.49182)

dat <- data.frame(Longitude, Latitude, MyGeo)

第二个按其纬度和纵向坐标具有邮政编码（由美国人口普查网站提供）。看起来像这样：

CensuseZip <- c("SomeZipCode1","SomeZipCode2","SomeZipCode3","SomeZipCode4","SomeZipCode5","SomeZipCode6","SomeZipCode7") 
Longitude2 <- c(-131.470425,-133.457924,-131.693453,-87.64957,-87.99734,-87.895,-88.0228)
Latitude2 <- c(55.138352,56.239062,56.370538,41.87485,42.0086,42.04957,41.81055)

cen <- data.frame(Longitude2, Latitude2,   CensuseZip)

现在，我相信第一个数据表为我提供了一个多边形或边界，我应该可以使用该多边形或边界来识别该边界内的邮政编码。理想情况下，我想创建一个看起来像这样的第三个数据表：

 Longitude2 Latitude2    CensusZip                        MyGeo
-131.470425 55.138352 SomeZipCode1  
-133.457924 56.239062 SomeZipCode2  
-131.693453 56.370538 SomeZipCode3
-87.64957    41.87485 SomeZipCode4  Part of Chicago & Wisconsin 
-87.99734     42.0086 SomeZipCode5  Part of Chicago & Wisconsin 
-87.895      42.04957 SomeZipCode6  Part of Chicago & Wisconsin 
-88.0228     41.81055 SomeZipCode7  Part of Chicago & Wisconsin 

从本质上讲，我正在寻找所有位于蓝色长点和纬度点之间的邮政编码（请参见下面的可点击图像）。如下图所示，我实际上正在寻找上述表格。

但是...我在执行此操作时遇到了麻烦...我尝试使用以下软件包和脚本：

library(rgeos)
library(sp)
library(rgdal)

coordinates(dat) <- ~ Longitude + Latitude
coordinates(cen) <- ~ Longitude2 + Latitude2

over(cen, dat)

但是我收到了所有NA。

Answer 1

我使用library(sf)解决了这种类型的多边形问题（sf是sp的后继者）。

函数sf::st_intersection()为您提供两个sf对象的交集。根据您的情况，您可以构造单独的POLYGON和POINT sf对象。

library(sf)

Longitude <- c(-90.31914,  -90.61911,  -89.37842,  -88.0988,  -87.44875)
Latitude <- c(38.45781, 38.80097, 43.07961, 43.0624,41.49182)

## closing the polygon
Longitude[length(Longitude) + 1] <- Longitude[1]
Latitude[length(Latitude) + 1] <- Latitude[1]

## construct sf POLYGON
sf_poly <- sf::st_sf( geometry = sf::st_sfc( sf::st_polygon( x = list(matrix(c(Longitude, Latitude), ncol = 2)))) )

## construct sf POINT
sf_points <- sf::st_as_sf( cen, coords = c("Longitude2", "Latitude2"))

sf::st_intersection(sf_points, sf_poly)

# Simple feature collection with 4 features and 1 field
# geometry type:  POINT
# dimension:      XY
# bbox:           xmin: -88.0228 ymin: 41.81055 xmax: -87.64957 ymax: 42.04957
# epsg (SRID):    NA
# proj4string:    NA
# CensuseZip                   geometry
# 4 SomeZipCode4 POINT (-87.64957 41.87485)
# 5 SomeZipCode5  POINT (-87.99734 42.0086)
# 6 SomeZipCode6   POINT (-87.895 42.04957)
# 7 SomeZipCode7  POINT (-88.0228 41.81055)
# Warning message:
#   attribute variables are assumed to be spatially constant throughout all geometries 

结果是多边形内的所有点

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您还可以使用sf::st_join(sf_poly, sf_points)给出相同的结果

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然后，函数sf::st_intersects(sf_points, sf_poly)将返回一个列表，说明给定的POINT是否在多边形内

sf::st_intersects(sf_points, sf_poly)

# Sparse geometry binary predicate list of length 7, where the predicate was `intersects'
#  1: (empty)
# 2: (empty)
# 3: (empty)
# 4: 1
# 5: 1
# 6: 1
# 7: 1

您可以用作原始sf_points对象的索引/标识符，以在其上添加新列

is_in <- sf::st_intersects(sf_points, sf_poly)

sf_points$inside_polygon <- as.logical(is_in)

sf_points
# Simple feature collection with 7 features and 2 fields
# geometry type:  POINT
# dimension:      XY
# bbox:           xmin: -133.4579 ymin: 41.81055 xmax: -87.64957 ymax: 56.37054
# epsg (SRID):    NA
# proj4string:    NA
# CensuseZip                   geometry inside_polygon
# 1 SomeZipCode1 POINT (-131.4704 55.13835)             NA
# 2 SomeZipCode2 POINT (-133.4579 56.23906)             NA
# 3 SomeZipCode3 POINT (-131.6935 56.37054)             NA
# 4 SomeZipCode4 POINT (-87.64957 41.87485)           TRUE
# 5 SomeZipCode5  POINT (-87.99734 42.0086)           TRUE
# 6 SomeZipCode6   POINT (-87.895 42.04957)           TRUE
# 7 SomeZipCode7  POINT (-88.0228 41.81055)           TRUE