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