如何填写 r 中 choropleth 的空白？ ggplot2 和地图

Question

谁能告诉我如何填写 choropleth 中的空白字段？我为我创建的合唱团附上了一张图片。非常感谢！

我注意到两个表中的 statename 不匹配，但我无法更改原始数据中的 statename。

library(ggplot2)
library(maps)
**#Data looks like this:**

aggrev2015<-data.frame(
statename=c("alabama","alaska","arizona","arkansas","california","colorado","connecticut","delaware","florida","georgia","hawaii","idaho","illinois","indiana","iowa","kansas","kentucky","louisiana","maine","maryland","massachusetts","michigan", "minnesota","mississippi","missouri","montana","nebraska","nevada","new hampshire","new jersey","new mexico","new york","north carolina","north dakota","ohio","oklahoma", "oregon","pennsylvania","rhode island","south carolina","south dakota","tennessee","texas","utah","vermont","virginia","washington","west virginia","wisconsin","wyoming"),
  revenue=runif(50,min=100,max=9000))

state_df <- map_data("state")
colnames(state_df)<-c("long","lat","group","order","statename","subregion")

choropleth <- merge(aggrev2015,state_df, by = "statename")

ggplot(choropleth, aes(long, lat, group = statename)) +
  geom_polygon(aes(fill = revenue))

Answer 1

乍一看，您的问题似乎与拥有岛屿的州有关。我不会调试它，而是跟进@hrbrmstr 使用 choroplethr 的建议：

library(choroplethr)
library(choroplethrMaps)

data(df_pop_state)
state_choropleth(df_pop_state)

您可以查看更多关于使用 choroplethr 包 here 创建状态 choropleth 的文档，该包也有一个 email course。

对于状态 choropleths，我认为包比自己做的主要优势在上面的小插图中得到了展示：它使探索性数据分析变得更加容易。例如，更改比例或缩放变得像在函数上设置参数一样简单。该软件包还包括 AK 和 HI 以及使用合理的投影。在 ggplot2 中自己解决这些问题往往是一件令人头疼的事情。请注意，我是 choroplethr 的作者，所以我是根据经验发言的 :)

要指出的另一件事是，您可能希望将等值线覆盖在参考地图上，例如来自谷歌地图的地图。我最近将该功能添加到最新版本的 choroplethr。但是我还没有机会更新包小插曲来解释如何使用它。要获取默认参考地图，只需设置reference_map = TRUE:

data(continental_us_states)
state_choropleth(df_pop_state, 
                 zoom = continental_us_states,
                 reference_map = TRUE)

如果您想使用不同的参考地图（例如卫星地图），您可以这样做。我刚刚在上面写了blog post。这是我几周前实施参考地图功能后遇到的最常见问题。