我一直在玩双变量 choropleth 地图，并且一直在如何创建类似于 2d 图例的问题上陷入困境约书亚·史蒂文斯 http://www.joshuastevens.net/cartography/make-a-bivariate-choropleth-map/此处显示：
为了说明这一挑战，我们不需要使用地图。下面的代码就足够了：
#test desired legend appearance
library(ggplot2)
library(reshape2)
#use color scheme shown here http://www.joshuastevens.net/cartography/make-a-bivariate-choropleth-map/
bvColors=c("#be64ac","#8c62aa","#3b4994","#dfb0d6","#a5add3","#5698b9","#e8e8e8","#ace4e4","#5ac8c8")
legendGoal=melt(matrix(1:9,nrow=3))
test<-ggplot(legendGoal, aes(Var1,Var2))+ geom_tile(aes(fill = as.factor(value)))
test<- test + scale_fill_manual(name="Var1 vs Var2",values=bvColors,drop=FALSE)
test
它创建的情节看起来像我想要的图例，但当然图例是所有级别的垂直条。我希望图例看起来像情节本身。有没有办法做到这一点？谢谢！
#test desired legend appearance
library(ggplot2)
library(reshape2)
#use color scheme shown here http://www.joshuastevens.net/cartography/make-a-bivariate-choropleth-map/
bvColors=c("#be64ac","#8c62aa","#3b4994","#dfb0d6","#a5add3","#5698b9","#e8e8e8","#ace4e4","#5ac8c8")
melt(matrix(1:9,nrow=3))
legendGoal=melt(matrix(1:9,nrow=3))
test<-ggplot(legendGoal, aes(Var2,Var1,fill = as.factor(value)))+ geom_tile()
test<- test + scale_fill_manual(name="More Var2 -->",values=bvColors,drop=FALSE)
test<-test+guides(fill = guide_legend(nrow = 3))
test<-test + theme(legend.text=element_blank())
test
唯一剩下的技巧是找到一种方法在图例的一侧添加一些垂直线，写着“More Var1 -->”。这是一个非常丑陋的方法：
test<-ggplot(legendGoal, aes(Var2,Var1,fill = as.factor(value)))+ geom_tile()
test<- test + scale_fill_manual(name="More Var2 -->",values=bvColors,labels=c("","","","","","","More","Var 1"," v "))
test<-test+guides(fill = guide_legend(nrow = 3))
#test<-test + theme(legend.text=element_blank())
test
但是，正如 zx 所示，使用owplot 包扩展 ggplot2 是完整的解决方案：
#test desired legend appearance
library(ggplot2)
library(cowplot)
library(reshape2)
#use color scheme shown here http://www.joshuastevens.net/cartography/make-a-bivariate-choropleth-map/
bvColors=c("#be64ac","#8c62aa","#3b4994","#dfb0d6","#a5add3","#5698b9","#e8e8e8","#ace4e4","#5ac8c8")
melt(matrix(1:9,nrow=3))
legendGoal=melt(matrix(1:9,nrow=3))
test<-ggplot(legendGoal, aes(Var2,Var1,fill = as.factor(value)))+ geom_tile()
test<- test + scale_fill_manual(name="",values=bvColors)
test<-test+guides(fill = guide_legend(nrow = 3))
test<-test + theme(legend.text=element_blank())
test<-ggdraw(test) + draw_text(text = "More Var 2 -->",x=0.91,y=0.58)
test<-ggdraw(test) + draw_text(text = "More Var 1 -->",x=0.84,y=0.5,angle=270)
test
Just for fun this is the map that I made with this technique:
