我有两个数据框，一个包含纬度/长点，另一个包含绘制多个多边形的geojson数据。
第一个数据框（countyDF）是从CSV导入的，第二个数据框（basin）是使用readLines（）从geoJSON导入的（我应该使用getJSON（）代替json数据吗？
即。 （通过简化的lat和long，让我知道一个更现实的例子是否有帮助） countyDF
pointNum Lat Long
1 100 251
2 150 175
3 50 -330
4 -150 100
和geoJSON格式如下（basin）：
{
"type": "FeatureCollection",
"crs": { "type": "name", "properties": { "name": "urn:ogc:def:crs:OGC:1.3:CRS84" } },
"features": [
{ "type": "Feature", "properties": { "Basin_ID": "9-19", "Basin_Subb": "9-19", "Basin_Name": "TIA JUANA", "Subbasin_N": null }, "geometry": { "type": "MultiPolygon", "coordinates": [ [ [ [ -117.0679768595155, 32.574291366336219 ], [ -117.06716593683379, 32.573400317874729 ], [ -117.06341997467541, 32.569091397019029 ], [ -117.06194315333148, 32.566356289257612 ], [ -117.0590009947062, 32.565022113434004 ], [ -117.05426277324793, 32.561991889800737 ], [ -117.04796901017907, 32.559156827796407 ], [ -117.03949416454982, 32.555722526353854 ], [ -117.03658670964059, 32.55260623337746 ], [ -117.03547505795123, 32.551186682532702 ], [ -117.03106791328587, 32.547633284977714 ], [ -117.02453341519558, 32.542766715943806 ], [ -117.03096733611001, 32.542203418941845 ], [ -117.0324558562139, 32.542073586201752 ], [ -117.03444148063983, 32.541897693349327 ], [ -117.03508530679723, 32.541840746762325 ], [ -117.03893675722108, 32.541503138385245 ], [ -117.04563848478635, 32.540916090254136 ], [ 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{ "type": "Feature", "properties": { "Basin_ID": "9-18", "Basin_Subb": "9-18", "Basin_Name": "OTAY VALLEY", "Subbasin_N": null }, "geometry": { "type": "MultiPolygon", "coordinates": [ [ [ [ -117.09094993890868, 32.619563585315568 ], [ -117.09024988989258, 32.616130450534968 ], [ -117.08912052342582, 32.606956836308925 ], [ -117.08936013555311, 32.601840287378998 ], [ -117.08875364427725, 32.598575478052986 ], [ -117.08680278644947, 32.595962898606246 ], [ -117.08441502669503, 32.595310423365085 ], [ -117.08156822333883, 32.595469231360795 ], [ -117.07566674287644, 32.595559902113109 ], [ -117.06972154230749, 32.596914588847568 ], [ -117.06432122834885, 32.598375496484095 ], [ -117.05964154380946, 32.598503627441907 ], [ -117.05616095566411, 32.597465378923445 ], [ -117.05457753753359, 32.596282762027229 ], [ -117.05073717232032, 32.594157791168556 ], [ -117.04589484061222, 32.592852213251177 ], [ -117.04312260910274, 32.593353146236865 ], [ -117.03899112955028, 32.593759832413419 ], [ 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]
}
我想针对所有＆＃34; Basin_ID＆＃34;测试点数1,2,3,4，如果它们在该盆地内，则将其作为列添加到countyDF。
例如，如果第1点位于第9-18区，并且其他任何一点都不属于盆地数据中包含的多边形，则返回的数据框将如下所示......
returnedDF：
pointNum Lat Long Basin
1 100 251 9-18
2 150 175 n/a
3 50 -330 n/a
4 -150 100 n/a
有人可能会建议一个特定的库/方法/解决方案来实现这个目标吗？我想如果有一个库可以测试一个点是否在多边形中，我可以遍历每个点的第二个数据帧吗？
答案 0 :(得分：1)
以下是一种可以执行此操作的方法，使用rgdal读取geojson（see this answer for more details on this）和sp和/或rgeos来测试点是否位于多边形与否。
注意，我调整了你的坐标，因为它们都没有位于多边形内。
首先，阅读数据：
countyDF <- read.table(textConnection("
pointNum Lat Long
1 32.6 -117.1
2 90 175
4 -90 100"), header = TRUE)
basinDF <- rgdal::readOGR("basin.json", "OGRGeoJSON")
确保点和多边形具有相同的投影：
sp::coordinates(countyDF) <- ~Long+Lat
sp::proj4string(countyDF) <- sp::proj4string(basinDF)
在这里，我们使用sp::over在每个点提取basinDF的属性。如果点不在basinDF NA的多边形内，则返回。
sp::over(countyDF, basinDF)
# Basin_ID Basin_Subb Basin_Name Subbasin_N
# 1 9-18 9-18 OTAY VALLEY <NA>
# 2 <NA> <NA> <NA> <NA>
# 3 <NA> <NA> <NA> <NA>
或者，您也可以使用rgeos，它告诉您第1点位于poygon 1中。
rgeos::gWithin(countyDF, basinDF, byid = TRUE)
# 1 2 3
# 0 FALSE FALSE FALSE
# 1 TRUE FALSE FALSE