Fix/onedimensional sigma for kernels (#499)

* add error message when passing high dimensional sigma to kernel, add handling of 1-dimensional kernel with size one

* add test raiseError for multidimensional sigma, add test for handling one-dimensional sigma of size 1

* add check for size

elephant/kernels.py

@@ -132,6 +132,10 @@ class Kernel(object):
     TypeError
         If `sigma` is not `pq.Quantity`.
 
+        If `sigma` is a multidimensional array
+
+    ValueError
+
         If `sigma` is negative.
 
         If `invert` is not `bool`.
@@ -142,6 +146,13 @@ def __init__(self, sigma, invert=False):
         if not isinstance(sigma, pq.Quantity):
             raise TypeError("'sigma' must be a quantity")
 
+        if sigma.ndim > 0:
+            # handle the one-dimensional case of size 1
+            if sigma.ndim == 1 & sigma.size == 1:
+                sigma = sigma[0]
+            else:
+                raise TypeError("'sigma' cannot be multidimensional")
+
         if sigma.magnitude < 0:
             raise ValueError("'sigma' cannot be negative")
 

elephant/test/test_kernels.py

@@ -31,8 +31,13 @@ def test_error_kernels(self):
         """
         Test of various error cases in the kernels module.
         """
-        self.assertRaises(
-            TypeError, kernels.RectangularKernel, sigma=2.0)
+        # pass multidimensional sigma
+        self.assertRaises(TypeError, kernels.RectangularKernel,
+                          sigma=[2.0, 2.3] * pq.s)
+        # pass one-dimensional sigma, this should be handled
+        self.assertEqual(
+            kernels.RectangularKernel(sigma=[2.0] * pq.s).sigma.ndim, 0)
+        self.assertRaises(TypeError, kernels.RectangularKernel, sigma=2.0)
         self.assertRaises(
             ValueError, kernels.RectangularKernel, sigma=-0.03 * pq.s)
         self.assertRaises(