From 37edeb896d202c1ce48bcaffdd40bc0cf5f7e5fe Mon Sep 17 00:00:00 2001
From: josidd <joseph.siddons@noc.ac.uk>
Date: Tue, 24 Sep 2024 15:31:18 +0100
Subject: [PATCH] feat: add find_nearest function
---
GeoSpatialTools/neighbours.py | 44 +++++++++++++++++++++++++++++++++++
1 file changed, 44 insertions(+)
create mode 100644 GeoSpatialTools/neighbours.py
diff --git a/GeoSpatialTools/neighbours.py b/GeoSpatialTools/neighbours.py
new file mode 100644
index 0000000..d13b637
--- /dev/null
+++ b/GeoSpatialTools/neighbours.py
@@ -0,0 +1,44 @@
+from numpy import argmin
+from bisect import bisect
+from typing import TypeVar
+from datetime import date, datetime
+
+
+Numeric = TypeVar("Numeric", int, float, datetime, date)
+
+
+def _find_nearest(vals: list[Numeric], test: Numeric) -> int:
+ i = bisect(vals, test) # Position that test would be inserted
+
+ # Handle edges
+ if i == 0 and test <= vals[0]:
+ return 0
+ elif i == len(vals) and test >= vals[-1]:
+ return len(vals) - 1
+
+ test_idx = [i - 1, i]
+ return test_idx[argmin([abs(test - vals[j]) for j in test_idx])]
+
+
+def find_nearest(vals: list[Numeric], test: list[Numeric]) -> list[int]:
+ """
+ Find the nearest value in a list of values for each test value.
+
+ Uses bisection for speediness!
+
+ Arguments
+ =========
+ vals : list[Numeric]
+ List of values - this is the pool of values for which we are looking
+ for a nearest match. This list MUST be sorted. Sortedness is not
+ checked, nor is the list sorted. An error will be raised if the list
+ is not sorted.
+ test : list[Numeric]
+ List of query values
+
+ Returns
+ =======
+ A list containing the index of the nearest neighbour in vals for each value
+ in test.
+ """
+ return [_find_nearest(vals, t) for t in test]
--
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