r ggplot2：在条形图中对图例进行分组

Question

我尝试使用ggplot2分别使用fill和alpha对barplot中的两个离散变量进行可视化。这样做的标准方法如下：

#creating data and building the basic bar plot 
library(ggplot2) 
myleg<-read.csv(text="lett,num 
a,1 
a,2 
b,1 
b,2 
h,1 
h,2 
h,3 
h,4") 
ggplot(myleg,aes(lett,alpha=factor(num),fill=lett)) +geom_bar(position=position_stack(reverse=T)) +scale_alpha_discrete(range=c(1,.1), name="alpha legend",labels=c("alpha lab 4","alpha lab 3","alpha lab 2", "alpha lab 1")) +labs(title="initial bar plot for data") 

默认图例是根据呈现的两种不同的方式进行分组（着色为快报和灰度，或不透明度为NUM）。

我需要将图例分组为数据条。即三个色带，每个色带具有不断变化的α级别。部分解决方案是，分别生成与期望的3图例条情节如下：

ggplot(myleg,aes(lett,alpha=factor(num),fill=lett)) +geom_bar(position="stack",fill="#f8766d") +scale_alpha_discrete(name="red legend",labels=c("red lab 2","red lab 1"),breaks=c("3","4")) 
ggplot(myleg,aes(lett,alpha=factor(num),fill=lett)) +geom_bar(position="stack",fill="#00ba38") +scale_alpha_discrete(name="green legend",labels=c("green lab 2","green lab 1"),breaks=c("3","4")) 
ggplot(myleg,aes(lett,alpha=factor(num),fill=lett)) +geom_bar(position="stack",fill="#619cff") +scale_alpha_discrete(name="blue legend",labels=c("blue lab 4","blue lab 3","blue lab 2", "blue lab 1")) 

输出：

所以现在我只能切割和三个图例条粘贴到主图形，例如，在Inkscape中，以产生期望的结果：

它是如何可能在一个体面的方式来编程吗？

Answer 1

可以绘制使用scale_fill_manual定制的传说：

df <- mtcars 
df$cyl <- factor(df$cyl) 
df$vs <- factor(df$vs) 

library(ggplot2)  
p <- ggplot(df,aes(x=cyl, fill=interaction(cyl,vs))) + geom_bar(position="stack") 

# Breaks 
brks <- levels(interaction(df$cyl,df$vs)) 

# Values - Colors 
library(scales) 
pal <- hue_pal()(3) 
cls <- as.character(c(sapply(pal,alpha,0.3),sapply(pal,alpha,1))) 

# Labels 
lbls <- paste(levels(df$cyl), "-", rep(levels(df$vs),each=3)) 

p + scale_fill_manual(name ='Cyl - Vs', breaks=brks, values=cls, labels=lbls) 

编辑这里被张贴@astrsk的（新的）问题的解决方案（他/她的变化后，最初的问题）。下面

library(ggplot2) 
library(grid) 
library(gridExtra) 
myleg <- structure(list(lett = structure(c(1L, 1L, 2L, 2L, 3L, 3L, 3L, 
3L), .Label = c("a", "b", "h"), class = "factor"), num = c(1L, 
2L, 1L, 2L, 1L, 2L, 3L, 4L)), .Names = c("lett", "num"), 
class = "data.frame", row.names = c(NA, -8L)) 

getLegend <- function(p) { 
    g <- ggplotGrob(p) 
    k <- which(g$layout$name=="guide-box") 
    g$grobs[[k]] 
} 

p1 <- ggplot(myleg,aes(lett,alpha=factor(num),fill=lett)) +geom_bar(position="stack",fill="#f8766d") +scale_alpha_discrete(name="red legend",labels=c("red lab 2","red lab 1"),breaks=c("3","4")) 
p2 <- ggplot(myleg,aes(lett,alpha=factor(num),fill=lett)) +geom_bar(position="stack",fill="#00ba38") +scale_alpha_discrete(name="green legend",labels=c("green lab 2","green lab 1"),breaks=c("3","4")) 
p3 <- ggplot(myleg,aes(lett,alpha=factor(num),fill=lett)) +geom_bar(position="stack",fill="#619cff") +scale_alpha_discrete(name="blue legend",labels=c("blue lab 4","blue lab 3","blue lab 2", "blue lab 1")) 

p <- ggplot(myleg,aes(lett,alpha=factor(num),fill=lett)) + 
    geom_bar(position=position_stack(reverse=T)) + 
    scale_alpha_discrete(range=c(1,.1), name="alpha legend", 
     labels=c("alpha lab 4","alpha lab 3","alpha lab 2", "alpha lab 1")) + 
    labs(title="initial bar plot for data") 
g <- ggplotGrob(p) 

k <- which(g$layout$name=="guide-box") 
g$grobs[[k]] <- grid.arrange(getLegend(p1),getLegend(p2),getLegend(p3),ncol=1) 
grid.draw(g)