如何在ggplot2的條形圖中更改堆疊順序？

Question

從online bar chart guide：

qplot(factor(cyl), data=mtcars, geom="bar", fill=factor(gear)) 

如何獲得5坐底，4上面，和3在上面？

Answer 1

qplot(factor(cyl), data=mtcars, geom="bar", fill=factor(gear), order = -gear)

Answer 2

qplot(factor(cyl), data=mtcars, geom='bar', fill=factor(gear, level=5:3)) 

Answer 3

要概括@ xiechao的解決方案（@哈德利的不最新ggplot工作），你可以扭轉因素的訂單來實現：

library(ggplot2) 
data(mtcars) 
mtcars$gear <- factor(mtcars$gear) # First make factor with default levels 
mtcars$gear <- factor(mtcars$gear, levels=rev(levels(mtcars$gear))) 
qplot(cyl, data=mtcars, geom="bar", fill=gear) 
# Or with ggplot 
ggplot(mtcars, aes(factor(cyl), fill=gear)) + geom_bar()