[Scipy-svn] r7029 - in trunk/scipy/stats: . tests

[scipy-svn at scipy.org]

Author: josef
Date: 2011-01-14 14:55:28 -0600 (Fri, 14 Jan 2011)
New Revision: 7029

Modified:
   trunk/scipy/stats/distributions.py
   trunk/scipy/stats/tests/test_distributions.py
Log:
stats.distributions expect:  fix bound handling and add tests for discrete distributions

Modified: trunk/scipy/stats/distributions.py
===================================================================
--- trunk/scipy/stats/distributions.py	2011-01-14 19:21:00 UTC (rev 7028)
+++ trunk/scipy/stats/distributions.py	2011-01-14 20:55:28 UTC (rev 7029)
@@ -5582,10 +5582,18 @@
         self._argcheck(*args) # (re)generate scalar self.a and self.b
         if lb is None:
             lb = (self.a)
+        else:
+            lb = lb - loc   #convert bound for standardized distribution
         if ub is None:
             ub = (self.b)
+        else:
+            ub = ub - loc   #convert bound for standardized distribution
         if conditional:
-            invfac = self.sf(lb,*args) - self.sf(ub+1,*args)
+            if np.isposinf(ub)[()]:
+                #work around bug: stats.poisson.sf(stats.poisson.b, 2) is nan
+                invfac = 1 - self.cdf(lb-1,*args)
+            else:
+                invfac = 1 - self.cdf(lb-1,*args) - self.sf(ub,*args)
         else:
             invfac = 1.0
 

Modified: trunk/scipy/stats/tests/test_distributions.py
===================================================================
--- trunk/scipy/stats/tests/test_distributions.py	2011-01-14 19:21:00 UTC (rev 7028)
+++ trunk/scipy/stats/tests/test_distributions.py	2011-01-14 20:55:28 UTC (rev 7029)
@@ -560,9 +560,11 @@
         assert_equal(m1, m2)
 
 class TestExpect(TestCase):
-    """Test for expect method, continuous distributions only.
+    """Test for expect method.
 
-    Uses normal distribution and beta distribution for finite bounds.
+    Uses normal distribution and beta distribution for finite bounds, and
+    hypergeom for discrete distribution with finite support
+
     """
     def test_norm(self):
         v = stats.norm.expect(lambda x: (x-5)*(x-5), loc=5, scale=2)
@@ -603,7 +605,55 @@
         assert_almost_equal(prob90c, 1., decimal=14)
 
 
+    def test_hypergeom(self):
+        #test case with finite bounds
 
+        #without specifying bounds
+        m_true, v_true = stats.hypergeom.stats(20, 10, 8, loc=5.)
+        m = stats.hypergeom.expect(lambda x: x, args=(20, 10, 8), loc=5.)
+        assert_almost_equal(m, m_true, decimal=14)
+        
+        v = stats.hypergeom.expect(lambda x: (x-9.)**2, args=(20, 10, 8),
+                                   loc=5.)
+        assert_almost_equal(v, v_true, decimal=14)
+
+        #with bounds, bounds equal to shifted support
+        v_bounds = stats.hypergeom.expect(lambda x: (x-9.)**2, args=(20, 10, 8),
+                                          loc=5., lb=5, ub=13)
+        assert_almost_equal(v_bounds, v_true, decimal=14)
+
+        #drop boundary points
+        prob_true = 1-stats.hypergeom.pmf([5, 13], 20, 10, 8, loc=5).sum()
+        prob_bounds = stats.hypergeom.expect(lambda x: 1, args=(20, 10, 8),
+                                          loc=5., lb=6, ub=12)
+        assert_almost_equal(prob_bounds, prob_true, decimal=14)
+
+        #conditional
+        prob_bc = stats.hypergeom.expect(lambda x: 1, args=(20, 10, 8), loc=5.,
+                                           lb=6, ub=12, conditional=True)
+        assert_almost_equal(prob_bc, 1, decimal=14)
+
+        #check simple integral
+        prob_b = stats.hypergeom.expect(lambda x: 1, args=(20, 10, 8),
+                                        lb=0, ub=8)
+        assert_almost_equal(prob_b, 1, decimal=14)
+
+    def test_poisson(self):
+        #poisson, use lower bound only
+        prob_bounds = stats.poisson.expect(lambda x: 1, args=(2,), lb=3,
+                                      conditional=False)
+        prob_b_true = 1-stats.poisson.cdf(2,2)
+        assert_almost_equal(prob_bounds, prob_b_true, decimal=14)
+        
+
+        prob_lb = stats.poisson.expect(lambda x: 1, args=(2,), lb=2,
+                                       conditional=True)
+        assert_almost_equal(prob_lb, 1, decimal=14)
+
+        
+
+
+
 def test_regression_ticket_1316():
     """Regression test for ticket #1316."""
     # The following was raising an exception, because _construct_default_doc()