R语言 ggplot2改变柱状图的顺序操作

library(ggplot2)
library(ggthemes)
dt = data.frame(obj = c('A','D','B','E','C'), val = c(2,15,6,9,7))
dt$obj = factor(dt$obj, levels=c('D','B','C','A','E')) ## 设置柱条的顺序
p = ggplot(dt, aes(x = obj, y = val, fill = obj, group = factor(1))) + 
geom_bar(stat = "identity", width = 0.5) + ## 修改柱条的宽度 
theme_economist()
p
## 特注：dt$obj 是因子类型，ggplot2作图的顺序就是按照这个因子水平的顺序来的，
## 所以我们修改因子水平的顺序即可修改作图的顺序，具体情况可以输出一下 dt$obj 

ggplot(upc, aes(x = Abb, y = Change)) +
geom_col(fill = "#669933")

ggplot(upc, aes(x = reorder(Abb,Change), y = Change)) +
geom_col(fill = "#669933")

ggplot(upc, aes(x = reorder(Abb, - Change), y = Change)) +
geom_col(fill = "#669933")