每行列名称前3个数据框R

Question

Let us say we have the following data frame in R:

DF <- as.data.frame.matrix(matrix(sample(1:15,15),ncol=5,nrow=3))

   V1  V2 V3 V4 V5
1  15   8  3 14  4
2  11   2  5 13  6
3   9   7 10 12  1

I'm trying to retrieve the column name of the top three values per row. I would like to get a new data frame with the following information:

1 V1 V4 V2
2 V4 V1 V5
3 V4 V3 V1

I tried by using apply and dapply but it is not working. I designed a function to use in apply but it is not working as expected. Could you give me any hint to tackle this. I think this should be of help.

Answer 1

We can loop through the rows ( apply with MARGIN=1 ), get the numeric index of the elements in the row decreasingly with order , use that to order the column names, get the first 3 elements with head , transpose the output and convert to data.frame .

 as.data.frame(t(apply(DF, 1, function(x) 
   head(names(DF)[order(-x)],3))), stringsAsFactors=FALSE)
#  V1 V2 V3
#1 V1 V4 V2
#2 V4 V1 V5
#3 V4 V3 V1