[MRG] Fix average_dipoles to allow for one trial

doc/whats_new.rst

@@ -41,6 +41,8 @@ Bug
 
 - Fix bug where depth of L5 and L2 cells were swapped, by `Christopher Bailey`_ in `#352 <https://github.com/jonescompneurolab/hnn-core/pull/352>`_
 
+- Fix bug where :func:`~hnn_core.average_dipole` failed when there were less than two dipoles in the input dipole list, by `Kenneth Loi`_ in `#368 <https://github.com/jonescompneurolab/hnn-core/pull/368>`_
+
 API
 ~~~
 - New API for defining cell-cell connections. Custom connections can be added with :func:`~hnn_core.Network.add_connection`, by `Nick Tolley`_ in `#276 <https://github.com/jonescompneurolab/hnn-core/pull/276>`_

hnn_core/dipole.py

@@ -112,12 +112,11 @@ def average_dipoles(dpls):
         A new dipole object with each component of `dpl.data` representing the
         average over the same components in the input list
     """
-    # need at least one Dipole to get times
-    if len(dpls) < 2:
-        raise ValueError("Need at least two dipole object to compute an"
-                         " average")
-
     for dpl_idx, dpl in enumerate(dpls):
+        if not isinstance(dpl, Dipole):
+            raise ValueError(
+                f"All elements in the list should be instances of "
+                f"Dipole. Got {type(dpl)}")
         if dpl.nave > 1:
             raise ValueError("Dipole at index %d was already an average of %d"
                              " trials. Cannot reaverage" %

hnn_core/tests/test_dipole.py

@@ -56,7 +56,27 @@ def test_dipole(tmpdir, run_hnn_core_fixture):
                        "average of 2 trials"):
         dipole_avg = average_dipoles([dipole_avg, dipole_read])
 
+    # average an n_of_1 dipole list
+    single_dpl_avg = average_dipoles([dipole])
+    for dpl_key in single_dpl_avg.data.keys():
+        assert_allclose(
+            dipole_read.data[dpl_key],
+            single_dpl_avg.data[dpl_key],
+            rtol=0,
+            atol=0.000051)
+
+    # average dipole list with one dipole object and a zero dipole object
+    n_times = len(dipole_read.data['agg'])
+    dpl_null = Dipole(np.zeros(n_times, ), np.zeros((n_times, 3)))
+    dpl_1 = [dipole, dpl_null]
+    dpl_avg = average_dipoles(dpl_1)
+    for dpl_key in dpl_avg.data.keys():
+        assert_allclose(dpl_1[0].data[dpl_key] / 2., dpl_avg.data[dpl_key])
+
+    # test postproc
+
     # XXX all below to be deprecated in 0.3
+
     dpls_raw, net = run_hnn_core_fixture(backend='joblib', n_jobs=1,
                                          reduced=True, record_isoma=True,
                                          record_vsoma=True)