Random samples from each column of a data.frame

Question

I want to draw random sample from each row of a data.frame independently from other rows. Here is an example. This code selects the same column for each row but I require independent selection of columns for each row.

library(plyr)
set.seed(12345)
df1 <- mdply(data.frame(mean=c(10, 15)), rnorm, n = 5, sd = 1)
df1
  mean       V1       V2        V3        V4       V5
1   10 10.58553 10.70947  9.890697  9.546503 10.60589
2   15 13.18204 15.63010 14.723816 14.715840 14.08068
> df1[ , -1]
        V1       V2        V3        V4       V5
1 10.58553 10.70947  9.890697  9.546503 10.60589
2 13.18204 15.63010 14.723816 14.715840 14.08068
> sample(df1[, -1], replace = TRUE)
         V3       V2       V5        V4      V4.1
1  9.890697 10.70947 10.60589  9.546503  9.546503
2 14.723816 15.63010 14.08068 14.715840 14.715840
> t(apply(df1[, -1], 1, sample))
         [,1]      [,2]     [,3]     [,4]      [,5]
[1,] 10.70947  9.890697 10.60589 10.58553  9.546503
[2,] 14.71584 13.182044 14.08068 15.63010 14.723816

Edited

df1[ , -1]
            V1       V2        V3        V4       V5
    1 10.58553 10.70947  9.890697  9.546503 10.60589
    2 13.18204 15.63010 14.723816 14.715840 14.08068

sample(df1[, -1], replace = TRUE)
             V3       V2       V5        V4      V4.1
    1  9.890697 10.70947 10.60589  9.546503  9.546503
    2 14.723816 15.63010 14.08068 14.715840 14.715840

sample(df1[, -1], replace = TRUE) selects the columns V3, V2, V5, V4, and V4 for both rows. But I require that it could select columns V3, V2, V5, V4, and V4 for first row and/or any combinations of five columns for second row.

Answer 1

You could use apply with replace=TRUE for the sample

 t(apply(df1[,-1], 1, sample, replace=TRUE))