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rsortingapplytranspose

How to sort each row of a data frame WITHOUT losing the column names

I'd like to sort each row of a data frame without losing the column names in R.
I know that this accepted answer works, but this method doesn't keep the names, as shown below:

data_5x3.csv

A,B,C,D,E
5,1,3,2,8
4,3,9,1,6
7,5,2,9,4

My code:

df <- read.csv("data_5x3.csv")

df
#   A B C D E
# 1 5 1 3 2 8
# 2 4 3 9 1 6
# 3 7 5 2 9 4

names(df)
# [1] "A" "B" "C" "D" "E"

sorted_df <- t(apply(df, 1, sort))

sorted_df
#       [,1] [,2] [,3] [,4] [,5]
# [1,]    1    2    3    5    8
# [2,]    1    3    4    6    9
# [3,]    2    4    5    7    9

names(sorted_df)
# NULL

Now the names are gone.
How can we prevent from losing the names?

Solution

  • Store the names and apply them:

    nm = names(df)
sorted_df <- as.data.frame(t(apply(df, 1, sort)))
names(sorted_df) = nm

    You could compress this down to a single line if you prefer:

    sorted_df = setNames(as.data.frame(t(apply(df, 1, sort))), names(df))