根据中值对盒子图进行排序

Question

我想用R来制作一系列按中值排序的箱形图.假设我执行:

boxplot(cost ~ type)

这将给我一些箱形图,成本显示在y轴上,类型类别在x轴上可见:

-----     -----
  |         |
 [ ]        |
  |        [ ]
  |         |
-----     -----
  A         B

但是,我想要的是从最高到最低中值排序的箱线图.我怀疑的是,我需要做的是更改类型(A或B)的标签,以数字方式指示哪个是最低和最高中值,但我想知道是否有更聪明的方法来解决问题.

Answer 1

退房?reorder.这个例子似乎是你想要的,但是以相反的顺序排序.我-count在下面的第一行更改了按您想要的顺序排序.

  bymedian <- with(InsectSprays, reorder(spray, -count, median))
  boxplot(count ~ bymedian, data = InsectSprays,
          xlab = "Type of spray", ylab = "Insect count",
          main = "InsectSprays data", varwidth = TRUE,
          col = "lightgray")

Answer 2

是的,这就是想法:

> set.seed(42)                     # fix seed       
> DF <- data.frame(type=sample(LETTERS[1:5], 100, replace=TRUE), 
+                  cost=rnorm(100)) 
>
> boxplot(cost ~ type, data=DF)    # not ordered by median
>
> # compute index of ordered 'cost factor' and reassign          
> oind <- order(as.numeric(by(DF$cost, DF$type, median)))    
> DF$type <- ordered(DF$type, levels=levels(DF$type)[oind])   
>
> boxplot(cost ~ type, data=DF)    # now it is ordered by median