- test-statistics.arr: added tests for the new stats functions brownp…

…lt#1732

- statistics.arr: added exceptions for t-test-{pooled, independent}

src/arr/trove/statistics.arr

@@ -229,7 +229,7 @@ fun t-test-paired(l1 :: List, l2 :: List) -> Number:
   if n1 <> n2:
     raise(E.message-exception("t-test-paired: input lists must have equal lengths"))
   else if n1 == 0:
-    raise(E.message-exception("t-test-paired: input lists should have at least one element"))
+    raise(E.message-exception("t-test-paired: input lists must have at least one element"))
   else:
     diffs = map2(lam(x1, x2): x1 - x2 end, l1, l2)
     diffs-mean = mean(diffs)
@@ -242,22 +242,30 @@ fun t-test-pooled(l1 :: List, l2 :: List) -> Number:
   doc: "t-test-pooled"
   n1 = l1.length()
   n2 = l2.length()
-  m1 = mean(l1)
-  m2 = mean(l2)
-  v1 = variance-sample(l1)
-  v2 = variance-sample(l2)
-  (m1 - m2) / (((((n1 - 1) * num-expt(v1, 2)) + ((n2 - 1) * num-expt(v2, 2))) / ((n1 + n2) - 2)) * num-sqrt((1 / n1) + (1 / n2)))
+  if (n1 == 0) or (n2 == 0):
+    raise(E.message-exception("t-test-pooled: input lists must have at least one element"))
+  else:
+    m1 = mean(l1)
+    m2 = mean(l2)
+    v1 = variance-sample(l1)
+    v2 = variance-sample(l2)
+    (m1 - m2) / (((((n1 - 1) * num-expt(v1, 2)) + ((n2 - 1) * num-expt(v2, 2))) / ((n1 + n2) - 2)) * num-sqrt((1 / n1) + (1 / n2)))
+  end
 end
 
 fun t-test-independent(l1 :: List, l2 :: List) -> Number:
   doc: "t-test-independent"
   n1 = l1.length()
   n2 = l2.length()
-  m1 = mean(l1)
-  m2 = mean(l2)
-  v1 = variance-sample(l1)
-  v2 = variance-sample(l2)
-  (m1 - m2) / num-sqrt((v1 / n1) + (v2 / n2))
+  if (n1 == 0) or (n2 == 0):
+    raise(E.message-exception("t-test-independent: input lists must have at least one element"))
+  else:
+    m1 = mean(l1)
+    m2 = mean(l2)
+    v1 = variance-sample(l1)
+    v2 = variance-sample(l2)
+    (m1 - m2) / num-sqrt((v1 / n1) + (v2 / n2))
+  end
 end
 
 fun chi-square(obs :: List, exp :: List) -> Number:

tests/pyret/tests/test-statistics.arr

@@ -49,18 +49,40 @@ check "numeric helpers":
   modes([list: -1, 2, -1, 2, -1]) is [list: -1]
   modes([list: 1, 1, 2, 2, 3, 3, 3]) is [list: 3]
 
+  variance([list:]) raises "empty"
+  variance([list: 5]) is 0
+  variance([list: 3, 4, 5, 6, 7]) is%(within(0.01)) 2.0
+  variance([list: 1, 1, 1, 1]) is-roughly ~0
+
   stdev([list:]) raises "empty"
   stdev([list: 5]) is 0
-
   stdev([list: 3, 4, 5, 6, 7]) is%(within(0.01)) 1.41
   stdev([list: 1, 1, 1, 1]) is-roughly ~0
-  stdev([list:]) raises "empty"
-
+
+  variance-sample([list: 3, 4, 5, 6, 7]) is%(within(0.01)) (10 / 4)
+  variance-sample([list: 3]) raises "division by zero"
+  variance-sample([list: 1, 1, 1, 1]) is-roughly ~0
+  variance-sample([list:]) raises "empty"
+
   stdev-sample([list: 3, 4, 5, 6, 7]) is%(within(0.01)) num-sqrt(10 / 4)
   stdev-sample([list: 3]) raises "division by zero"
   stdev-sample([list: 1, 1, 1, 1]) is-roughly ~0
   stdev-sample([list:]) raises "empty"
 
+  t-test-paired([list: 1], [list: 2, 3]) raises "lists must have equal lengths"
+  t-test-paired([list:], [list:]) raises "lists must have at least one element"
+  t-test-paired([list: 1, 2, 3], [list: 4, 6, 8]) is%(within(0.01)) -6.928
+
+  t-test-pooled([list:], [list: 1, 2, 3]) raises "lists must have at least one element"
+  t-test-pooled([list: 1, 2, 3], [list: 4, 5, 6]) is%(within(0.01)) -3.674
+  t-test-pooled([list: 1, 2, 3], [list: 4, 5, 6, 7]) is%(within(0.01)) -2.217
+
+  t-test-independent([list:], [list: 1, 2, 3]) raises "lists must have at least one element"
+  t-test-independent([list: 1, 2, 3], [list: 4, 5, 6]) is%(within(0.01)) -3.674
+  t-test-independent([list: 1, 2, 3], [list: 4, 5, 6, 7]) is%(within(0.01)) -4.041
+
+  chi-square([list: 1, 2, 3, 4], [list: 1, 2, 3, 4]) is 0
+  chi-square([list: 1, 2, 3, 4], [list: 0.9, 1.8, 3.5, 4.7]) is%(within(0.01)) 0.209
 end
 
 check "linear regression":