Question

Say that I have 4 numpy arrays
[1,2,3]
[2,3,1]
[3,2,1]
[1,3,2]

In this case, I’ve determined [1,2,3] is the “minimum array” for my purposes, as it is one of two arrays with lowest value at index 0, and of those two arrays it has the the lowest index 1. If there were more arrays with similar values, I would need to compare the next index values, and so on.

How can I extract the array [1,2,3] in that same order from the pile?

How can I extend that to x arrays of size n?

Thanks

Answer 1

Using the python non-numpy .sort() or sorted() on a list of lists (not numpy arrays) automatically does this e.g.

a = [[1,2,3],[2,3,1],[3,2,1],[1,3,2]]
a.sort()

gives

[[1,2,3],[1,3,2],[2,3,1],[3,2,1]]

The numpy sort seems to only sort the subarrays recursively so it seems the best way would be to convert it to a python list first. Assuming you have an array of arrays you want to pick the minimum of you could get the minimum as

sorted(a.tolist())[0]

As someone pointed out you could also do min(a.tolist()) which uses the same type of comparisons as sort, and would be faster for large arrays (linear vs n log n asymptotic run time).