All possible sample combinations from a list

Grasshopper
1

Hello,

I would like your insight on a problem I have. It might be simple but I’m stuck. Let’s say I have a list of 10 items and I want to get all possible combinations of a sample of 5 items from them. Any ideas how to do this?

Thank you

2

Hi,

Here is a possibility with Cross Reference

The result is a tree with (10 choose 5) = 252 branches.

image
image1056×361 36.5 KB

FiveChooseTen.gh (10.3 KB)

3

Thank you, it seems to work. Are you aware if there is a limit to the number of items grasshopper can calculate? For example, if I bump the list to 20 items and the sample to 10, that would generate 184756 branches of 10 items, 1847560 in total.

4

The amount of items is not a problem, but the Cross Reference component seems to be extremely slow, so I made a C# component to do the job - takes less than 10 seconds.

However it is absolutely not practical to modify the number of items chosen, I’m sure something better exists.

TenChooseTwenty.gh (15.0 KB)

5

There we (there we (there we (there we… go) go) go) go

(with recursion).

RecursiveNChoosek.gh (8.5 KB)

6

Get the general case.

Entry level: works on collections of Type int (*) for 6 results: permutations/combinations/kcombos/cats and dogs.

PermutationsAndCombinations_V1.gh (120.7 KB)

(*) but the Methods used accept any Type - see inside

7

Thank you everybody for your valuable help!