使用列表对ggplot的x轴进行排序。

Question

我有一个数据框，想要将其作为条形图绘制，但我希望分类的x值按照我指定的列表顺序进行排序。我将使用mtcars数据集示例说明。

#get a small version of the mtcars dataset and add a named column
mtcars2 <- mtcars
mtcars2[["car"]] <- rownames(mtcars2)
mtcars2 <- mtcars[0:5,]
# I would like to plot this using the following
p = ggplot(mtcars2, aes(x=car, y=mpg))+ geom_bar(stat="identity")

x轴的值按字母顺序排序。但如果我有一列汽车名单，我希望ggplot保留这个顺序怎么办：

#list out of alphabetical order
orderlist = c("Hornet 4 Drive", "Mazda RX4 Wag", "Mazda RX4",
               "Datsun 710", "Hornet Sportabout") 

# I would like to plot the bar graph as above but preserve the plot order
# something like this:
p = ggplot(mtcars2, aes(x= reorder( car, orderlist), y=mpg))+ geom_bar(stat="identity")

任何指导都将不胜感激， zach cp

- zach

Answer 1

将 car 因子的水平设置为你想要的顺序，例如：

mtcars2 <- transform(mtcars2, car = factor(car, levels = orderlist))

那么情节就会在没有进一步干预的情况下运作：

ggplot(mtcars2, aes(x=car, y=mpg))+ geom_bar(stat="identity")

- Gavin Simpson