BUG: fix kaiser for M=1.

2 files changed, 11 insertions, 9 deletions

diff --git a/numpy/lib/function_base.py b/numpy/lib/function_base.py
index 76ea08dfb..7b0984a03 100644
--- a/numpy/lib/function_base.py
+++ b/numpy/lib/function_base.py
@@ -2612,6 +2612,8 @@ def kaiser(M,beta):
 
     """
     from numpy.dual import i0
+    if M == 1:
+        return np.array([1.])
     n = arange(0,M)
     alpha = (M-1)/2.0
     return i0(beta * sqrt(1-((n-alpha)/alpha)**2.0))/i0(float(beta))
diff --git a/numpy/lib/tests/test_function_base.py b/numpy/lib/tests/test_function_base.py
index 8595c6b5c..af5feadc7 100644
--- a/numpy/lib/tests/test_function_base.py
+++ b/numpy/lib/tests/test_function_base.py
@@ -772,15 +772,15 @@ class Test_i0(TestCase):
 
 class TestKaiser(TestCase):
     def test_simple(self):
-        assert_almost_equal(kaiser(0,1.0), array([]))
-        assert isnan(kaiser(1,1.0))
-        assert_almost_equal(kaiser(2,1.0), array([ 0.78984831,  0.78984831]))
-        assert_almost_equal(kaiser(5,1.0),
-                            array([ 0.78984831,  0.94503323,  1.        ,
-                                    0.94503323,  0.78984831]))
-        assert_almost_equal(kaiser(5,1.56789),
-                            array([ 0.58285404,  0.88409679,  1.        ,
-                                    0.88409679,  0.58285404]))
+        assert_almost_equal(kaiser(0, 1.0), array([]))
+        assert isfinite(kaiser(1, 1.0))
+        assert_almost_equal(kaiser(2, 1.0), array([ 0.78984831, 0.78984831]))
+        assert_almost_equal(kaiser(5, 1.0),
+                            array([ 0.78984831, 0.94503323, 1.        ,
+                                    0.94503323, 0.78984831]))
+        assert_almost_equal(kaiser(5, 1.56789),
+                            array([ 0.58285404, 0.88409679, 1.        ,
+                                    0.88409679, 0.58285404]))
 
     def test_int_beta(self):
         kaiser(3, 4)