我有一个像下面这样的数据框：
State<-c("Alabama","Alabama","Alaska","Alaska")
StateCode<-c("AL","AL","AK","AK")
County<-c("AUTAUGA","BALDWIN","ANCHORAGE","BETHEL")
CountyCode<-c("AL001","AL003","AK020","AK050")
Murder<-c(5,6,7,8)
d<-data.frame(State,StateCode,County,CountyCode, Num)
State StateCode County CountyCode Num
1 Alabama AL AUTAUGA AL001 5
2 Alabama AL BALDWIN AL003 6
3 Alaska AK ANCHORAGE AK020 7
4 Alaska AK BETHEL AK050 8
我一直在寻找R包之间的选项，以创建一个从州到县级的向下钻取图，但是我找不到任何地方有代码的有效示例。这是example对此有任何反馈吗？