无法添加新图层

Question

我有一个代表旧金山邮政编码区的情节。

# Download San Francisco zip codes polygons
path="http://moshetoronto.free.fr/blog/sfreal/geo_export_f72cfa08-0728-4a0b-bbcc-1fafc25de0f5.shp"
filename="geo_export_f72cfa08-0728-4a0b-bbcc-1fafc25de0f5.shp"
download.file(path,filename, mode = "wb")
pathfile=paste0(getwd(),"/",filename)

# load the file
getwd()
sfn = readOGR(dsn =pathfile ) %>% spTransform(CRS("+proj=longlat +datum=WGS84"))
sfn.f<- sfn %>% fortify

# build the map
mysfn <- ggplot(data = sfn.f, aes(x=long, y=lat, group = id)) +
  geom_polygon(fill="white",alpha=1) +
  geom_path(color = "black",size=0.05,alpha=0.15)

我得到了假点的数据框：

# build the dataframe
myds=data.frame("long"=sample(seq(-122.35,-122.5,0.01),size = 10,replace=FALSE),
                "lat"=sample(seq(37.7,37.80,0.01),size = 10,replace=FALSE))

我只想在地图上映射这些点：

# try to draw a contour plot
mysfn + geom_point( data=myds, aes(x=long,y=lat),colour="red")

但它不起作用，我收到此错误消息：

  

eval（expr，envir，enclos）中的错误：找不到对象'id'