Sorting one variable in a data frame by id

Question

I have a data frame with lot of company information separated by an id variable. I want to sort one of the variables and repeat it for every id. Let's take this example,

df <- structure(list(id = c(110, 110, 110, 90, 90, 90, 90, 252, 252
), var1 = c(26, 21, 54, 10, 18, 9, 16, 54, 39), var2 = c(234, 
12, 43, 32, 21, 19, 16, 34, 44)), .Names = c("id", "var1", "var2"
), row.names = c(NA, -9L), class = "data.frame")

Which looks like this

df
   id var1 var2
1 110   26  234
2 110   21   12
3 110   54   43
4  90   10   32
5  90   18   21
6  90    9   19
7  90   16   16
8 252   54   34
9 252   39   44

Now, I want to sort the data frame according to var1 by the vector id. Easiest solution I can think of is using apply function like this,

> apply(df, 2, sort)
       id var1 var2
 [1,]  90    9   12
 [2,]  90   10   16
 [3,]  90   16   19
 [4,]  90   18   21
 [5,] 110   21   32
 [6,] 110   26   34
 [7,] 110   39   43
 [8,] 252   54   44
 [9,] 252   54  234

However, this is not the output I am seeking. The correct output should be,

   id var1 var2
1 110   21   12
2 110   26  234
3 110   54   43
4  90    9   19
5  90   10   32
6  90   16   16
7  90   18   21
8 252   39   44
9 252   54   34

Group by id and sort by var1 column and keep original id column order.

Any idea how to sort like this?

Answer 1

使用order和的另一个基本R选项match

df[with(df, order(match(id, unique(id)), var1, var2)), ]
#   id var1 var2
#2 110   21   12
#1 110   26  234
#3 110   54   43
#6  90    9   19
#4  90   10   32
#7  90   16   16
#5  90   18   21
#9 252   39   44
#8 252   54   34

Answer 2

注意。如Moody_Mudskipper所述，无需使用tidyverse，也可以使用base轻松完成R：

df[order(ordered(df$id, unique(df$id)), df$var1), ]

没有tidyverse任何temp变量的单线解决方案：

library(tidyverse)
df %>% arrange(ordered(id, unique(id)), var1)
#    id var1 var2
# 1 110   26  234
# 2 110   21   12
# 3 110   54   43
# 4  90   10   32
# 5  90   18   21
# 6  90    9   19
# 7  90   16   16
# 8 252   54   34
# 9 252   39   44

为什么apply(df, 2, sort)不起作用的解释

您试图做的是对每个列进行独立排序。apply在指定的维度上运行（2在这种情况下，它对应于列）并应用函数（sort在这种情况下）。

apply尝试进一步简化结果，在这种情况下简化为矩阵。因此，您将获得一个矩阵（不是 a data.frame），其中每一列都是独立排序的。例如，apply呼叫中的这一行：

# [1,]  90    9   12

甚至根本不存在data.frame。