I agree with Mike here. This is a trivial function, if somebody needs it as a function they can generate a function handle when needed.

I also suggest closing it as "wont fix".

I am only offering my opinion as a member of the Octave community. I am leaving this open for now for others to weigh in.

My opinion is that this function should not be added to Octave, mainly for compatibility reasons.

There are two compatibility reasons to consider:

1. When Octave invents a new function that is not already in Matlab, there is a potential for Matlab to create a function in the future that conflicts with it.

The mitigation for this is that Octave chooses names that are not likely to be used by Matlab. For this case, I would suggest a name like "num_ordered_subsets" or "num_sequences_without_repetition".

2. Matlab does not provide the function that you are looking for, so anyone familiar with Matlab or who wants to write scripts that are compatible with Matlab already must express this in terms of factorial, nchoosek, or pochhammer. Since Octave already supports all of those functions, we are fully compatible. If Octave introduces a new function, users who want to remain Matlab compatible will have to avoid using it.

Additionally, I am not a mathematician, but I gather there is some naming confusion about permutations vs ordered subsets vs sequences without repetition. If this function were added to Octave, it would probably be best to avoid using the word permutation for this function, because permutations are orderings of the complete set, not subsets, i.e. factorial(n).

Thank you Dildar.Your code serves my purpose but I think this function should be implemented as built in.
And I don't think there is any compatibility issue in implementing this function.There is many trivial functions,which is 'simple' to calculate.

I don't believe Matlab has a function for the number of permutations without repetition. And since it is such a simple expression to calculate based on nchoosek, I doubt there is a need for us to invent a function where Matlab hasn't already done so.

Leaning towards closing as wont fix.

I doubt it,
Whatever if there is no inbuilt function available
please add my m-file what implemented.
m-file is attached.

(file #43498)