使用反向地理编码功能时如何处理缺失值？

Question

我目前在 R 中使用 data（N of 271,848），如下所示：

Observation   Longitude     Latitude
--------------------------------------
      1        116.38800    39.928902
      2        53.000000    32.000000
      3          NA          NA
      4          NA          NA

我正在使用以下帖子中的反向地理编码功能：Convert latitude and longitude coordinates to country name in R

当我运行coords2country(points) 行时，我收到以下错误：

“.checkNumericCoerce2double(obj) 中的错误：非有限坐标”

我最好的猜测是该函数不知道如何处理缺失值。当我在观察的子集（不包括 NA/缺失值）上运行代码时，它可以工作。

我试图稍微修改函数（见下面的最后一行）来解决这个问题，但这仍然产生了我上面提到的错误。

可重现的例子：

Data <- data.frame(
  Observation = 1:5,
  Longitude = c(116.3880005, 53, -97, NA, NA), 
  Latitude = c(39.92890167, 32, 32, NA, NA))

library(sp)
library(rworldmap)
    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 +datum=wgs84"))
      #! andy modified to make the CRS the same as rworldmap
      #pointsSP = SpatialPoints(points, proj4string=CRS("+proj=longlat +ellps=WGS84 +datum=WGS84 +no_defs"))
      # new changes in worldmap means you have to use this new CRS (bogdan):
      pointsSP = SpatialPoints(points, proj4string=CRS(" +proj=longlat +ellps=WGS84 +datum=WGS84 +no_defs +towgs84=0,0,0"))

      # 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
      #The line below is what I thought could resolve the problem.
      na.action = na.omit
        }

Answer 1

最好改用这个：

coords2country_NAsafe <- function(points)
{
    bad <- with(points, is.na(lon) | is.na(lat))
    result <- character(length(bad))
    result[!bad] <- coords2country(points[!bad,])
    result
}