Menu
Every time I have to do this I "invent" a different way. Time to standardize. I suspect there is some default command I overlooked ready to do this, so I am sorry in advance if the question is too trivial.
What is the better (memory, performance) way to get:
combinations[{1,2,3},2] = {{1,2},{1,3},{2,3}}
with arbitrary elements in the input list, of course.
203
Enter the formula =List1. Expand out the new List1 column and then Close & Load the query to a table. The table will have all the combinations of items from both lists and we saved on making a custom column in List1 and avoided using a merge query altogether!
The algorithm assumes that we have a set containing elements: {0, 1, … , }. Then, we generate the subsets containing elements in the form , starting from the smallest lexicographic order: The algorithm visits all -combinations. It recursively represents multiple nested for loops.
Subsets[{1, 2, 3}, {2}]
is the built-in way.
110
Before Subsets was added as a core function, the Combinatorica function KSubsets was available.
Needs["Combinatorica`"]
KSubsets[{1, 2, 3}, 2]
(* {{1, 2}, {1, 3}, {2, 3}} *)
Combinatorica still provides additional functionality, such as NextKSubset:
NextKSubset[{1, 2, 3}, {1, 3}]
(* {2, 3} *)
This last function can be very helpful for memory management.
28
If you love us? You can donate to us via Paypal or buy me a coffee so we can maintain and grow! Thank you!
Donate Us With
