geowatch.utils.util_kwutil module¶

Functions that may be moved to kwutil

geowatch.utils.util_kwutil.distributed_subitems(items, max_num)[source]¶

Return a subset of items maximally distributed over the input index space. I.e. the chosen indexes are maximally dialted.

Parameters:: items (List | Dict) – an ordered indexable object
Returns:: a subset of the input with a length at most max_num.
Return type:: List | Dict

Todo

[ ] Find a better name
[ ] Figure out where this lives

Example

>>> from geowatch.utils.util_kwutil import *  # NOQA
>>> items = list(range(100))
>>> max_num = 5
>>> sub_items = distributed_subitems(items, max_num)
>>> print(sub_items)
[0, 25, 50, 75, 99]

Example

>>> from geowatch.utils.util_kwutil import *  # NOQA
>>> items = {chr(i): i for i in range(ord('a'), ord('a') + 26)}
>>> max_num = 5
>>> sub_items = distributed_subitems(items, max_num)
>>> print(sub_items)
{'a': 97, 'g': 103, 'n': 110, 't': 116, 'z': 122}

geowatch.utils.util_kwutil.farthest_from_previous(start, stop)[source]¶

Given a ordered list of items, incrementally yield indexes such that each new index maximizes the distance to all other previously chosen indexes.

Parameters:

start (int) – The inclusive starting index (typically 0)
stop (int) – The exclusive maximum index (typically len(items))

Yields:

int – the next chosen index in the series

Todo

[ ] Find a Better Name

Notes

This is an instance of farthest-point traversal in 1D.

References

[CSSE_167943]

https://cs.stackexchange.com/questions/167943/is-this-knapsack-variant-named-studied-online-algorithm-for-farthest-from-pr

CommandLine

xdoctest -m geowatch.utils.util_kwutil farthest_from_previous

Example

>>> from geowatch.utils.util_kwutil import *  # NOQA
>>> total = 10
>>> start, stop = 0, 10
>>> gen = farthest_from_previous(start, stop)
>>> result = list(gen)
>>> assert set(result) == set(range(start, stop))
>>> print(result)
[9, 0, 5, 2, 7, 1, 6, 3, 8, 4]