提问者:小点点

使用反向地理编码函数时,如何处理丢失的值?


我目前正在使用R中的数据(271,848的N),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函数:在 R 中将纬度和经度坐标转换为国家/地区名称

当我运行< code > coords 2 country(points)行时,我得到以下错误:

". check NumericCoerce2bean(obj):非有限坐标中的错误"

我的最佳猜测是该函数不知道如何处理丢失的值。当我对观察值的子集(不包括NA/缺失值)运行代码时,它工作了。

我试图稍微修改这个函数(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
        }

共1个答案

匿名用户

最好用这个代替:

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