Sorting one variable in a data frame by id - r

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

Note. As mentioned by Moody_Mudskipper, there is no need to use tidyverse and can also be done easily with base R:
df[order(ordered(df$id, unique(df$id)), df$var1), ]
A one-liner tidyverse solution w/o any temp vars:
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
Explanation of why apply(df, 2, sort) does not work
What you were trying to do is to sort each column independently. apply runs over the specified dimension (2 in this case which corresponds to columns) and applies the function (sort in this case).
apply tries to further simplify the results, in this case to a matrix. So you are getting back a matrix (not a data.frame) where each column is sorted independently. For example this row from the apply call:
# [1,] 90 9 12
does not even exist in the original data.frame.

Answer 2

Another base R option using order and 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 3

We can convert the id to factor in order to split while preserving the original order. We can then loop over the list and order, and rbind again, i.e.
df$id <- factor(df$id, levels = unique(df$id))
do.call(rbind, lapply(split(df, df$id), function(i)i[order(i$var1),]))
# id var1 var2
#110.2 110 21 12
#110.1 110 26 234
#110.3 110 54 43
#90.6 90 9 19
#90.4 90 10 32
#90.7 90 16 16
#90.5 90 18 21
#252.9 252 39 44
#252.8 252 54 34
NOTE: You can reset the rownames by rownames(new_df) <- NULL

Answer 4

In base R we could use split<- :
split(df,df$id) <- lapply(split(df,df$id), function(x) x[order(x$var1),] )
or as #Markus suggests :
split(df, df$id) <- by(df, df$id, function(x) x[order(x$var1),])
output in either case :
df
# 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

Answer 5

With the following tidyverse pipe, the question's output is reproduced.
library(tidyverse)
df %>%
mutate(tmp = cumsum(c(0, diff(id) != 0))) %>%
group_by(id) %>%
arrange(tmp, var1) %>%
select(-tmp)
## A tibble: 9 x 3
## Groups: id [3]
# id var1 var2
# <dbl> <dbl> <dbl>
#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