Reputation: 454
This is an R programming question. I would like to rearrange the order of columns in a data frame based on the values in one of the rows. Here is an example data frame:
df <- data.frame(A=c(1,2,3,4),B=c(3,2,4,1),C=c(2,1,4,3),
D=c(4,2,3,1),E=c(4,3,2,1))
Suppose I want to rearrange the columns in df based on the values in row 4, ascending from 1 to 4, with ties having the same rank. So the desired data frame could be:
df <- data.frame(B=c(3,2,4,1),D=c(4,2,3,1),E=c(4,3,2,1),
C=c(2,1,4,3),A=c(1,2,3,4))
although I am indifferent about the order of first three columns, all of which have the value 1 in column 4.
I could do this with a for loop, but I am looking for a simpler approach. Thank you.
Upvotes: 2
Views: 432
Reputation: 886948
We can use select
- subset the row (4), unlist
, order
the values and pass it on select
library(dplyr)
df %>%
select(order(unlist(.[4, ])))
-output
B D E C A
1 3 4 4 2 1
2 2 2 3 1 2
3 4 3 2 4 3
4 1 1 1 3 4
Or may use
df %>%
select({.} %>%
slice_tail(n = 1) %>%
flatten_dbl %>%
order)
B D E C A
1 3 4 4 2 1
2 2 2 3 1 2
3 4 3 2 4 3
4 1 1 1 3 4
or in base R
df[order(unlist(tail(df, 1))),]
Upvotes: 1