使用反向地址解析功能时如何处理缺失值? [英] How to handle missing values when using a reverse geocode function?

问题描述

我目前正在R中使用数据(N为271,848)如下所示:

I am currently working with data (N of 271,848) in R that looks as follows:

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址解析功能:

And I am using a reverse geocode function from the following post: Convert latitude and longitude coordinates to country name in R

运行coords2country(points)行时，出现以下错误:

When I run the coords2country(points) line, I get the following error:

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

"Error in .checkNumericCoerce2double(obj) : non-finite coordinates"

我的最佳猜测是该函数不知道如何处理缺失值.当我对观察值的一个子集(不适用NA/缺失值)运行代码时，它可以工作.

My best guess is that the function does not know how to treat missing values. When I run the code on a subset of observations (excluding NA's/missing values), it works.

我试图稍作修改功能(请参见下面的最后一行)以解决此问题，但是仍然产生我在上面提到的错误.

I attempted to modify the function slightly (see last line below) to fix this problem, but that still produced the error I am referring to above.

可复制的示例:

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
        }

推荐答案

最好改用它:

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

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