Rearrange two columns so that the first column values are always larger in R

user_12096107 0
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I have two columns that holds integers. I need to rearrange the columns so that the first column values are always larger

The example input:

     co1 co2
[1,]  15  25
[2,]  35  55
[3,]  65  45
[4,]  40  50

The desired output:

     co1 co2
[1,]  25  15
[2,]  55  35
[3,]  65  45
[4,]  50  40

Any help will be appreciated.

r
3 Answers

A base R one-liner is

mat[] <- t(apply(mat, 1, sort, decreasing = TRUE))
mat
#     co1 co2
#[1,]  25  15
#[2,]  55  35
#[3,]  65  45
#[4,]  50  40

Data

mat <-
structure(c(25L, 55L, 65L, 50L, 15L, 35L, 45L, 40L), 
.Dim = c(4L, 2L), .Dimnames = list(NULL, c("co1", "co2")))
user_82454060

We can also use pmin/pmax from base R

cbind(pmax(mat[,1], mat[,2]), pmin(mat[,1], mat[,2]))
#     [,1] [,2]
#[1,]   25   15
#[2,]   55   35
#[3,]   65   45
#[4,]   50   40

data

mat <- structure(c(25L, 55L, 65L, 50L, 15L, 35L, 45L, 40L), .Dim = c(4L, 
2L), .Dimnames = list(NULL, c("co1", "co2")))
user_37322710

My solution is as follows:

for(i in 1:dim(df)[1]){
  if(df[i,1]<df[i,2]){
    df[i,1]->store
    df[i,2]->df[i,1]
    store->df[i,2]
  }
}

However, I am sure that there is an elegant solution in a line!

user_120961070
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