We can use the bijection mentioned in the wikipedia article, which maps combinations without repetition of type n+k-1 choose k to k-multicombinations of size n. We generate the combinations without repetition and map them using bsxfun(@minus, nchoosek(1:n+k-1,k), 0:k-1);. This results in the following function: function combs = nmultichoosek(values, k) %// Return number of multisubsets or … Read more
Counters are a kind of multiset. From the Counter() documentation: Several mathematical operations are provided for combining Counter objects to produce multisets (counters that have counts greater than zero). Addition and subtraction combine counters by adding or subtracting the counts of corresponding elements. Intersection and union return the minimum and maximum of corresponding counts. Each … Read more
I just added this feature to Guava, see here for the Javadoc. Edit: usage example of Multisets.copyHighestCountFirst() as per the original question: Multiset<DeviceType> histogram = getDeviceStats(); for (DeviceType type : Multisets.copyHighestCountFirst(histogram).elementSet()) { System.out.println(type + “: ” + histogram.count(type)); }
On Python 2, the comparison falls back to the default sort order for dictionaries (Counter is a subclass of dict). Mappings (dictionaries) compare equal if and only if their sorted (key, value) lists compare equal. [5] Outcomes other than equality are resolved consistently, but are not otherwise defined. [6] On Python 3, the comparison raises … Read more
A Walk Through a Slice of Combinatorics in R* Below, we examine packages equipped with the capabilities of generating combinations & permutations. If I have left out any package, please forgive me and please leave a comment or better yet, edit this post. Outline of analysis: Introduction Combinations Permutations Multisets Summary Memory Before we begin, … Read more