相关疑难解决方法(0)

如何在ggplot2中的堆积条上方绘制每个类的总和值(在我的情况下:a = 450,b = 150,c = 290,d = 90)？这是我的代码:

#Data
hp=read.csv(textConnection(
"class,year,amount
a,99,100
a,100,200
a,101,150
b,100,50
b,101,100
c,102,70
c,102,80
c,103,90
c,104,50
d,102,90"))
hp$year=as.factor(hp$year)

#Plotting
p=ggplot(data=hp)  
p+geom_bar(binwidth=0.5,stat="identity")+  
aes(x=reorder(class,-value,sum),y=value,label=value,fill=year)+
theme()