r - 从 R 中的经纬度点获取国家(和大陆)

Question

作为 a question I posted yesterday 的后续行动, R 中是否有包/函数可以为我提供由经度和纬度定义的点所在的国家(和大陆)？ 与已完成的事情类似的事情 here in MatLab.

数据框看起来像这样......

Point_Name              Longitude   Latitude
University of Arkansas  36.067832   -94.173655
Lehigh University       40.601458   -75.360063
Harvard University      42.379393   -71.115897

我想输出上面添加了国家和大陆列的数据框。 作为额外奖励 , 一个列有美国各州的人在美国(和“其他”为美国以外的人)？

Answer 1

要获得大陆，您可以修改 coords2country 的最后一行函数使用 rworldmap从这里 answer创建一个 coords2continent功能如下图。选择您想要 6 大陆还是 7 大陆模型。我会考虑把这段代码放进rworldmap .

library(sp)
library(rworldmap)

# The single argument to this function, points, is a data.frame in which:
#   - column 1 contains the longitude in degrees
#   - column 2 contains the latitude in degrees
coords2continent = function(points)
{  
  countriesSP <- getMap(resolution='low')
  #countriesSP <- getMap(resolution='high') #you could use high res map from rworldxtra if you were concerned about detail

  # converting points to a SpatialPoints object
  # setting CRS directly to that from rworldmap
  pointsSP = SpatialPoints(points, proj4string=CRS(proj4string(countriesSP)))  


  # use 'over' to get indices of the Polygons object containing each point 
  indices = over(pointsSP, countriesSP)

  #indices$continent   # returns the continent (6 continent model)
  indices$REGION   # returns the continent (7 continent model)
  #indices$ADMIN  #returns country name
  #indices$ISO3 # returns the ISO3 code 
}

这是一个测试。

points = data.frame(lon=c(0, 90, -45, -100, 130), lat=c(52, 40, -10, 45, -30 ))

coords2continent(points)
#[1] Europe        Asia          South America North America Australia  
coords2country(points)
#[1] United Kingdom  China   Brazil   United States of America  Australia