根据给定列中值的出现次数重新排列dataframe的行

第一个例子：

a <- cbind(1:10, c("a","b","a","b","b","d","a","b", "d", "c"))
a
     [,1] [,2]
 [1,] "1"  "a" 
 [2,] "2"  "b" 
 [3,] "3"  "a" 
 [4,] "4"  "b" 
 [5,] "5"  "b" 
 [6,] "6"  "d" 
 [7,] "7"  "a" 
 [8,] "8"  "b" 
 [9,] "9"  "d" 
[10,] "10" "c" 

---

我目前正在使用一个非常难看的

来构建

循环，它基本上通过一个排序的

计数（a，2）

数据帧，然后重新构建一个新的数据帧。你知道如何更简洁地完成吗？

你可以使用

ave

和

order

使用

ave

计算每个“组”的长度，然后对结果排序<如果您关心领带，代码>排名可能也很有用

> a[order(ave(a[, 2], a[, 2], FUN = length), decreasing = TRUE), ]
      [,1] [,2]
 [1,] "2"  "b" 
 [2,] "4"  "b" 
 [3,] "5"  "b" 
 [4,] "8"  "b" 
 [5,] "1"  "a" 
 [6,] "3"  "a" 
 [7,] "7"  "a" 
 [8,] "6"  "d" 
 [9,] "9"  "d" 
[10,] "10" "c"

---

您可以使用

ave

和

order

使用

ave

计算每个“组”的长度，然后对结果排序<如果您关心领带，代码>排名可能也很有用

> a[order(ave(a[, 2], a[, 2], FUN = length), decreasing = TRUE), ]
      [,1] [,2]
 [1,] "2"  "b" 
 [2,] "4"  "b" 
 [3,] "5"  "b" 
 [4,] "8"  "b" 
 [5,] "1"  "a" 
 [6,] "3"  "a" 
 [7,] "7"  "a" 
 [8,] "6"  "d" 
 [9,] "9"  "d" 
[10,] "10" "c"

---

标题引用了

data.frame

。使用

data.table

和

dplyr

a1 <- as.data.frame(a)
library(data.table)
ans <- setDT(a1)[,N := .N, by = V2][order(-N)][, N := NULL]
#       V1 V2
#    1:  2  b
#    2:  4  b
#    3:  5  b
#    4:  8  b
#    5:  1  a
#    6:  3  a
#    7:  7  a
#    8:  6  d
#    9:  9  d
#   10: 10  c

---

标题引用了

data.frame

。使用

data.table

和

dplyr

a1 <- as.data.frame(a)
library(data.table)
ans <- setDT(a1)[,N := .N, by = V2][order(-N)][, N := NULL]
#       V1 V2
#    1:  2  b
#    2:  4  b
#    3:  5  b
#    4:  8  b
#    5:  1  a
#    6:  3  a
#    7:  7  a
#    8:  6  d
#    9:  9  d
#   10: 10  c

---

仅供参考：在本例中，您实际上有一个

矩阵

，而不是

data.frame

：-）仅供参考：在本例中，您实际上有一个

矩阵

，而不是

data.frame

：-）