r - sample column without duplicates -

i'm writing custom function achieve this, wondering if there simple, built-in function in r achieve same goals.

i have data like:

stringvariable1     stringvariable2  string1             string1             b string1             d string2             e string2             string3             b 

and want shuffle data in stringvariable2, don't want duplicates in respect different stringvariables in 1.

so wouldn't acceptable (as 'b' duplicated respect string1):

stringvariable1     stringvariable2  string1             b string1             b string1             d string2             string2             e string3             d 

but would:

stringvariable1     stringvariable2  string1             b string1             e string1             d string2             string2             e string3             d 

so i'm trying randomise stringvariable2, without replacement respect different stringvariable1's. creating custom function way this?

thanks!

are values of stringvariable2 duplicated in groups of stringvariable1? if not, group-wise permutation performed (d name of data frame containing data):

d$perm1<-as.vector(unlist(tapply(d$stringvariable2, d$stringvariable1, sample))) 

this (tapply()) applies sampling without replacement (using sample()) stringvariable2 inside every group of stringvariable1. finally, resulting list converted vector using unlist() , as.vector(). last function strips off names of observations inside vector. permuted values stored ìn column perm1 of original data frame.