I want to find all the possible combinations from a set of pairs. Nice algorithm without recursion borrowed from C. Recursion is elegant but iteration is efficient. With combinations, one does not consider the order in which objects were placed. Toggle Main Navigation. where n = 7 for my purposes and r is a changeable number of spots as I called it. This algorithm (program in Matlab) calculates the number of permutations and combinations of … Description. A permutation of a set of objects is an ordering of those objects. You should be able to manipulate the results of e.g., nchoosek(1:8, 2) to give you what you need. This example will help explaining the problem better. all combinations without repetition. Say I have this line of code: c=nchoosek(1:6,2) , it gives: When some of those objects are identical, the situation is transformed into a problem about permutations with repetition. Viewed 2k times 1. The combntns function provides the combinatorial subsets of a set of numbers. Say I have this line of code: c=nchoosek(1:6,2) , it gives: Ask Question Asked 5 years, 5 months ago. But then the last row breaks this. I want to find all the possible combinations from a set of pairs. ... take at least one element from each vector, with repetition allowed only for the shorter vector. All possible combinations of 2 vectors.. So you're looking at permuting 8 things: combinations of the 6 objects and the 2 dividers. In distinguishing between combinations allowing repetition and those not, I think it's a question of supply of the objects being selected that's important to consider. Learn more about combinations . combos = combntns(set,subset) returns a matrix whose rows are the various combinations that can be taken of the elements of the vector set of length subset.Many combinatorial applications can make use of a vector 1:n for the input set to return generalized, indexed combination subsets.. Without repetition is appropriate when supply is limited; with repetition when supply is unlimited. / (r! For maximum compatibility, this program uses only the basic instruction set (S/360) and two ASSIST macros (XDECO, XPRNT) to keep the code as short as possible. Skip to content. Combinations with repetitions You are encouraged to solve this task according to the task description, using any language you may know. Active 5 years, 5 months ago. Number of combinations w/ repetition is equal to (n + r - 1)! * (n-1)!) That's much more efficient than generating all combinations and choosing those with the correct sum. MATLAB: All combinations from a set of rows without repetition of elements. Generating all combinations without repetition using MATLAB. This example will help explaining the problem better. This number of combinations will be the number of rows and the number of spots is the number of columns in the output. – Mark Dickinson Feb 1 '14 at 16:54 So what is the rule? 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