错误与功能强化的GGPLOT2

Question

我收到此错误与方法强化在GGPLOT2：

Error in (function (classes, fdef, mtable) : unable to find an inherited method for function ‘proj4string’ for signature ‘"NULL"’

的代码如下：

> library(maptools) 
> gpclibPermit() 
> library(ggplot2) 
> library(rgdal) 
> library(rgeos) 
> library(ggmap) 
> brMap <- readShapePoly("Google/BRASIL.shp") 
> brMapDF <- fortify(brMap) 
# This actually works 

# But this don´t 

> brMapDF <- fortify(brMap, region="UF") 

Error in (function (classes, fdef, mtable) : 
      unable to find an inherited method for function ‘proj4string’ for signature ‘"NULL"’ 

这种情况与所有的shape文件是我有，所以我尝试了（在上面的代码中）与我在shapeoverflow中找到的shapefile，我发现在stackoverflow Format the ggplot2 map，数据是https://docs.google.com/file/d/0B_coFit6AovfcEFkbHBjZEJaQ1E/edit

Answer 1

这是一种解决方法，但是如果您在数据准备工作中将我的评论中的示例wiki中所示的UF列作为id列复制，则fortify的默认值将使用空间数据框中的第一列来分隔出相应的多边形，同时在id列下添加名称。

library(maptools) 
library(ggplot2) 
library(sp) 
library(rgdal) 
library(rgeos) 

brMap <- readShapePoly("Google/BRASIL", IDvar = "UF", 
    proj4string = CRS("+init=epsg:4236"), repair = TRUE, verbose = TRUE) 
brMap@data$id <- brMap@data$UF 
brMapDF <- fortify(brMap) 

为brMapDF所产生的结构则是：

'data.frame': 9316 obs. of 7 variables: 
$ long : num -68.6 -68.7 -68.8 -68.8 -68.9 ... 
$ lat : num -11.1 -11.2 -11.2 -11.1 -11.1 ... 
$ order: int 1 2 3 4 5 6 7 8 9 10 ... 
$ hole : logi FALSE FALSE FALSE FALSE FALSE FALSE ... 
$ piece: Factor w/ 37 levels "1","2","3","4",..: 1 1 1 1 1 1 1 1 1 1 ... 
$ group: Factor w/ 81 levels "AC.1","AL.1",..: 1 1 1 1 1 1 1 1 1 1 ... 
$ id : chr "AC" "AC" "AC" "AC" ...