Merge ff3261a into 278d1e6

nipy/modalities/fmri/design.py

@@ -9,6 +9,7 @@
 
 import numpy as np
 
+from nipy.utils import seq_prod_def
 from nipy.algorithms.statistics.utils import combinations
 from nipy.algorithms.statistics.formula import formulae
 from nipy.algorithms.statistics.formula.formulae import (
@@ -105,7 +106,7 @@ def _build_formula_contrasts(spec, fields, order):
         between factors.
     """
     e_factors = [Factor(n, np.unique(spec[n])) for n in fields]
-    e_formula = np.product(e_factors)
+    e_formula = seq_prod_def(e_factors)
     e_contrasts = {}
     # Add contrasts for factors and factor interactions
     max_order = min(len(e_factors), order)
@@ -115,7 +116,7 @@ def _build_formula_contrasts(spec, fields, order):
             # Collect factors where there is more than one level
             fs = [fc.main_effect for fn, fc in comb if len(fc.levels) > 1]
             if len(fs) > 0:
-                e_contrast = np.product(fs).design(spec)
+                e_contrast = seq_prod_def(fs).design(spec)
                 e_contrasts[":".join(names)] = e_contrast
     e_contrasts['constant'] = formulae.I.design(spec)
     return e_formula, e_contrasts

nipy/utils/__init__.py

@@ -29,7 +29,7 @@
 else:
     HAVE_TEMPLATES = True
 
-from .utilities import is_iterable, is_numlike, seq_prod
+from .utilities import is_iterable, is_numlike, seq_prod, seq_prod_def
 
 from nipy.testing import Tester
 test = Tester().test

nipy/utils/tests/test_utilities.py

@@ -8,7 +8,7 @@
                         assert_equal, assert_not_equal)
 
 
-from ..utilities import is_iterable, is_numlike, seq_prod
+from ..utilities import is_iterable, is_numlike, seq_prod, seq_prod_def
 
 def test_is_iterable():
     assert_true(is_iterable(()))
@@ -49,7 +49,18 @@ def test_is_numlike():
 
 def test_seq_prod():
     assert_equal(seq_prod(()), 1)
+    assert_equal(seq_prod((), 2), 2)
     assert_equal(seq_prod((1,)), 1)
     assert_equal(seq_prod((1, 2)), 2)
     assert_equal(seq_prod((1, 2), 2), 4)
     assert_equal(seq_prod((1, 2), 2.), 4.)
+
+
+def test_seq_prod_def():
+    assert_equal(seq_prod_def(()), 1)
+    assert_equal(seq_prod_def((), 2), 2)
+    assert_equal(seq_prod_def((1,)), 1)
+    assert_equal(seq_prod_def((1, 2)), 2)
+    # Differs from seq_prod
+    assert_equal(seq_prod_def((1, 2), 2), 2)
+    assert_equal(seq_prod_def((1, 2), 2.), 2)

nipy/utils/utilities.py

@@ -43,3 +43,24 @@ def seq_prod(seq, initial=1):
         Result of ``initial * seq[0] * seq[1] .. ``.
     """
     return reduce(mul, seq, initial)
+
+
+def seq_prod_def(seq, default=1):
+    """ Product of elements in `seq`, with `default` for empty `seq`.
+
+    Parameters
+    ----------
+    seq : sequence
+        Iterable of values to multiply.
+    default : object, optional
+        Value to return in case of empty sequence.
+
+    Returns
+    -------
+    prod : object
+        Value of `default` if `seq` is empty, otherwise result of ``seq[0] *
+        seq[1] .. ``.
+    """
+    if len(seq) == 0:
+        return default
+    return reduce(mul, seq)