"""Mathematical helpers."""
+import collections
import functools
import math
from heapq import heappop, heappush
-from typing import List, Optional
+from typing import Dict, List, Optional, Tuple
+
+import dict_utils
class NumericPopulation(object):
- """A running median computer.
+ """A numeric population with some statistics such as median, mean, pN,
+ stdev, etc...
>>> pop = NumericPopulation()
>>> pop.add_number(1)
>>> pop.get_mean()
5.2
>>> round(pop.get_stdev(), 2)
- 6.99
+ 1.75
>>> pop.get_percentile(20)
3
>>> pop.get_percentile(60)
7
+
"""
def __init__(self):
count = len(self.lowers) + len(self.highers)
return self.aggregate / count
+ def get_mode(self) -> Tuple[float, int]:
+ count: Dict[float, int] = collections.defaultdict(int)
+ for n in self.lowers:
+ count[-n] += 1
+ for n in self.highers:
+ count[n] += 1
+ return dict_utils.item_with_max_value(count)
+
def get_stdev(self) -> float:
"""Returns the stdev so far in O(n) time."""
variance += (n - mean) ** 2
for n in self.highers:
variance += (n - mean) ** 2
- return math.sqrt(variance)
+ count = len(self.lowers) + len(self.highers) - 1
+ return math.sqrt(variance) / count
def get_percentile(self, n: float) -> float:
"""Returns the number at approximately pn% (i.e. the nth percentile)