X-Git-Url: https://wannabe.guru.org/gitweb/?a=blobdiff_plain;f=math_utils.py;fp=math_utils.py;h=dd26cb6f175dea80ae28181c9cf983115b37f323;hb=f6ec577f04044f21076c4c24c6aa2ab784c6cfc9;hp=270df8ccb3e8a1fcd5ea3f955438f800fcb69807;hpb=fa101dcf585cc6578ed3fd9a0cea748c0114b59c;p=python_utils.git

diff --git a/math_utils.py b/math_utils.py
index 270df8c..dd26cb6 100644
--- a/math_utils.py
+++ b/math_utils.py
@@ -99,6 +99,15 @@ class NumericPopulation(object):
         count = len(self.lowers) + len(self.highers) - 1
         return math.sqrt(variance) / count
 
+    def _create_sorted_copy_if_needed(self, count: int):
+        if not self.sorted_copy or count != len(self.sorted_copy):
+            self.sorted_copy = []
+            for x in self.lowers:
+                self.sorted_copy.append(-x)
+            for x in self.highers:
+                self.sorted_copy.append(x)
+            self.sorted_copy = sorted(self.sorted_copy)
+
     def get_percentile(self, n: float) -> float:
         """Returns the number at approximately pn% (i.e. the nth percentile)
         of the distribution in O(n log n) time.  Not thread-safe;
@@ -108,15 +117,8 @@ class NumericPopulation(object):
         if n == 50:
             return self.get_median()
         count = len(self.lowers) + len(self.highers)
-        if self.sorted_copy is not None:
-            if count == len(self.sorted_copy):
-                index = round(count * (n / 100.0))
-                assert 0 <= index < count
-                return self.sorted_copy[index]
-        self.sorted_copy = [-x for x in self.lowers]
-        for x in self.highers:
-            self.sorted_copy.append(x)
-        self.sorted_copy = sorted(self.sorted_copy)
+        self._create_sorted_copy_if_needed(count)
+        assert self.sorted_copy
         index = round(count * (n / 100.0))
         assert 0 <= index < count
         return self.sorted_copy[index]