为绘图制作 2D 图例 - 双变量等值线图

Question

我一直在玩双变量 choropleth 地图，并且一直坚持如何创建类似于此处显示的 Joshua Stevens 的 2d 图例：

为了说明挑战，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

它创建了一个看起来像我想要的图例的情节，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！

Answer 1

#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

剩下的唯一技巧是想办法在“More Var1 -->”的图例一侧添加一些竖线。这是一种非常丑陋的做法：

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 cowplot 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

只是为了好玩，这是我用这种技术制作的地图：

Answer 2

不是一个完整的答案，但我认为您需要使用guides。

ggplot(legendGoal, 
       aes(Var1,Var2,
           col=as.factor(value),
           fill=as.factor(value))) +
  geom_tile() +
  guides(col = guide_legend(nrow = 3))

Answer 3

好的，最后一次更新。列之间的空白让我很烦，cowplot 的网格功能将让我们使用缩小的图作为我们的双变量图例，如下所示：

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 + theme(legend.position="none")
#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)

#create a plot that will be the legend itself
lg<- test #would not be true when making a map
lg<-lg + theme(axis.title.x=element_text(size=rel(1),color=bvColors[3])) + xlab("More Var2 -->")
lg<-lg + theme(axis.title.y=element_text(size=rel(1),color=bvColors[3])) + ylab("More Var1 -->")
lg<-lg+theme(axis.text=element_blank())
lg<-lg+theme(line=element_blank())
#put both plots on a grid
ggdraw()+ draw_plot(lg,0.1,0.7,width=0.2,height=0.2) +draw_plot(test,0.3,0,width=.7,height=.7)

漂亮，是吗？