Issue 138 - Adds functions to calculate the state distribution of a Match

axelrod/interaction_utils.py

@@ -9,6 +9,7 @@
 interactions.
 """
 import csv
+from collections import Counter
 
 from .game import Game
 from axelrod import Actions
@@ -87,6 +88,57 @@ def compute_normalised_cooperation(interactions):
     return normalised_cooperation
 
 
+def compute_state_distribution(interactions):
+    """
+    Returns the count of each state for a set of interactions.
+
+    Parameters
+    ----------
+    interactions : list of tuples
+        A list containing the interactions of the match as shown at the top of
+        this file.
+
+    Returns
+    ----------
+    Counter(interactions) : Counter Object
+        Dictionary where the keys are the states and the values are the number
+        of times that state occurs.
+    """
+    if not interactions:
+        return None
+    return Counter(interactions)
+
+
+def compute_normalised_state_distribution(interactions):
+    """
+    Returns the normalized count of each state for a set of interactions.
+
+    Parameters
+    ----------
+    interactions : list of tuples
+        A list containing the interactions of the match as shown at the top of
+        this file.
+
+    Returns
+    ----------
+    normalized_count : Counter Object
+        Dictionary where the keys are the states and the values are a normalized
+        count of the number of times that state occurs.
+    """
+    if not interactions:
+        return None
+
+    interactions_count = Counter(interactions)
+    total = sum(interactions_count.values(), 0.0)
+    # By starting the sum with 0.0 we make sure total is a floating point value,
+    # avoiding the Python 2 floor division behaviour of / with integer operands
+    # (Stack Overflow)
+
+    normalized_count = Counter({key: value / total for key, value in
+                                interactions_count.items()})
+    return normalized_count
+
+
 def sparkline(actions, c_symbol=u'█', d_symbol=u' '):
     return u''.join([
         c_symbol if play == 'C' else d_symbol for play in actions])

axelrod/match.py

@@ -159,6 +159,18 @@ def normalised_cooperation(self):
         """Returns the count of cooperations by each player per turn"""
         return iu.compute_normalised_cooperation(self.result)
 
+    def state_distribution(self):
+        """
+        Returns the count of each state for a set of interactions.
+        """
+        return iu.compute_state_distribution(self.result)
+
+    def normalised_state_distribution(self):
+        """
+        Returns the normalized count of each state for a set of interactions.
+        """
+        return iu.compute_normalised_state_distribution(self.result)
+
     def sparklines(self, c_symbol=u'█', d_symbol=u' '):
         return iu.compute_sparklines(self.result, c_symbol, d_symbol)
 

axelrod/tests/unit/test_interaction_utils.py

@@ -1,6 +1,7 @@
 # -*- coding: utf-8 -*-
 import unittest
 import tempfile
+from collections import Counter
 import axelrod
 import axelrod.interaction_utils as iu
 
@@ -17,6 +18,14 @@ class TestMatch(unittest.TestCase):
     winners = [False, 0, 1, None]
     cooperations = [(1, 1), (0, 2), (2, 1), None]
     normalised_cooperations = [(.5, .5), (0, 1), (1, .5), None]
+    state_distribution = [Counter({('C', 'D'): 1, ('D', 'C'): 1}),
+                          Counter({('D', 'C'): 2}),
+                          Counter({('C', 'C'): 1, ('C', 'D'): 1}),
+                          None]
+    normalised_state_distribution = [Counter({('C', 'D'): 0.5, ('D', 'C'): 0.5}),
+                                     Counter({('D', 'C'): 1.0}),
+                                     Counter({('C', 'C'): 0.5, ('C', 'D'): 0.5}),
+                                     None]
     sparklines = [ u'█ \n █', u'  \n██', u'██\n█ ', None ]
 
 
@@ -46,6 +55,14 @@ def test_compute_normalised_cooperations(self):
         for inter, coop in zip(self.interactions, self.normalised_cooperations):
             self.assertEqual(coop, iu.compute_normalised_cooperation(inter))
 
+    def test_compute_state_distribution(self):
+        for inter, dist in zip(self.interactions, self.state_distribution):
+            self.assertEqual(dist, iu.compute_state_distribution(inter))
+
+    def test_compute_normalised_state_distribution(self):
+        for inter, dist in zip(self.interactions, self.normalised_state_distribution):
+            self.assertEqual(dist, iu.compute_normalised_state_distribution(inter))
+
     def test_compute_sparklines(self):
         for inter, spark in zip(self.interactions, self.sparklines):
             self.assertEqual(spark, iu.compute_sparklines(inter))