[R] Writing a Permutation Function

[Sarah Goslee]

We really can't help you with your assignment. You might consider
??unique
though, since you've already resolved to look for functions related to identifying unique entries.

Sarah

On Apr 28, 2012, at 8:11 AM, petermec <petermec at buffalo.edu> wrote:

> Hi everyone, 
> 
> I am somewhat new to R and I am trying to write a permutation function such
> that it inputs a character vector and from an arbitrary length "n" which is
> the length of the combinations for the character vector. I know there are R
> packages for permutation but this is for an assignment.
> 
> So far this is what I have:
> 
> alphabet = c("a","b","c","d")
> spot = c()
> permute = function(alphabet,n){
> for (i in 1:factorial(length(alphabet))){
>    perm = sample(alphabet, replace=F, size=n)
>    spot = rbind(spot, perm, deparse.level=2)
> }
> print(spot)
> }
> 
> This function works but it has some flaws for what I need. I would like the
> print output to have the rownames as the combination of the characters for
> each row (ie aa for "a" "a"). Also, this code is producing duplicate
> combinations whereas I only want an output of unique combinations.
> 
> To address the rownames problem I have, I have been trying to meddle around
> with creating a dataframe from rbind with something like:
> data2 = data.frame(spot, check.names=TRUE) 
> 
> I was thinking something along the lines of this to remove duplicates:
> or something like make.unique(spot)
> or make.names(spot, unique=TRUE)
> 
> Neither of these have been working for me. Could someone help point me in
> the right direction?
> 
> Much appreciated.
> 
> 
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