转换纬度和经度坐标，以国名中的R(Convert latitude and longitude co

我有纬度和经度坐标的列表，并希望找出他们都居住在哪个国家。

我修改的答案从约LAT-长到美国各州这个问题，并有一个工作的功能，但我碰到的问题是， worldHires地图（从mapdata包）是令人发指的过时的并含有大量的这种过时的国家南斯拉夫和苏联。

我将如何修改此功能使用更现代化的包装，如rworldmap ？我只设法阻挠自己至今...

library(sp)
library(maps)
library(rgeos)
library(maptools)

# 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
coords2country = function(points)
{
    # prepare a SpatialPolygons object with one poly per country
    countries = map('worldHires', fill=TRUE, col="transparent", plot=FALSE)
    names = sapply(strsplit(countries$names, ":"), function(x) x[1])

    # clean up polygons that are out of bounds
    filter = countries$x < -180 & !is.na(countries$x)
    countries$x[filter] = -180

    filter = countries$x > 180 & !is.na(countries$x)
    countries$x[filter] = 180

    countriesSP = map2SpatialPolygons(countries, IDs=ids, proj4string=CRS("+proj=longlat +datum=wgs84"))


    # convert our list of points to a SpatialPoints object
    pointsSP = SpatialPoints(points, proj4string=CRS("+proj=longlat +datum=wgs84"))


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


    # Return the state names of the Polygons object containing each point
    myNames = sapply(countriesSP@polygons, function(x) x@ID)
    myNames[indices]
}

##
## this works... but it has obsolete countries in it
## 

# set up some points to test
points = data.frame(lon=c(0, 5, 10, 15, 20), lat=c(51.5, 50, 48.5, 47, 44.5))

# plot them on a map
map("worldHires", xlim=c(-10, 30), ylim=c(30, 60))
points(points$lon, points$lat, col="red")

# get a list of country names
coords2country(points)
# returns [1] "UK"         "Belgium"    "Germany"    "Austria"    "Yugoslavia"
# number 5 should probably be in Serbia...

Answer 1:

感谢您的精心构建的问题。它需要的只是一对夫妇的线转换为能够使用rworldmap（含上最新的国家）见下文。我不是CRS专家，但我不认为我必须做的proj4string的变化有什么差别。其他人可能会喜欢上发表评论。

这为我工作和给：

> coords2country(points)
[1] United Kingdom     Belgium            Germany            Austria           
[5] Republic of Serbia

所有最好的，安迪

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
coords2country = function(points)
{  
  countriesSP <- getMap(resolution='low')
  #countriesSP <- getMap(resolution='high') #you could use high res map from rworldxtra if you were concerned about detail

  # convert our list of points to a SpatialPoints object

  # pointsSP = SpatialPoints(points, proj4string=CRS(" +proj=longlat +ellps=WGS84 +datum=WGS84 +no_defs +towgs84=0,0,0"))

  #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)

  # return the ADMIN names of each country
  indices$ADMIN  
  #indices$ISO3 # returns the ISO3 code 
  #indices$continent   # returns the continent (6 continent model)
  #indices$REGION   # returns the continent (7 continent model)
}

Answer 2:

你可以使用我的geonames包从查找http://geonames.org/服务：

> GNcountryCode(51.5,0)
$languages
[1] "en-GB,cy-GB,gd"

$distance
[1] "0"

$countryName
[1] "United Kingdom of Great Britain and Northern Ireland"

$countryCode
[1] "GB"

> GNcountryCode(44.5,20)
$languages
[1] "sr,hu,bs,rom"

$distance
[1] "0"

$countryName
[1] "Serbia"

$countryCode
[1] "RS"

从R-锻造得到它，因为我不知道我不屑于它发布到CRAN：

https://r-forge.r-project.org/projects/geonames/

是的，它依赖于外部服务，但至少知道发生了什么共产主义... :)

文章来源: Convert latitude and longitude coordinates to country name in R