add labels_freq func; add test

hands_on/pyanno_voting/pyanno/tests/test_voting.py

@@ -41,3 +41,10 @@ def test_majority_vote_empty_item():
     expected = [1, MV, 2]
     result = voting.majority_vote(annotations)
     assert result == expected
+
+def test_label_freq():
+    result = voting.labels_frequency([[1, 1, 2], [-1, 1, 2]], 4)
+    expected = np.array([ 0. ,  0.6,  0.4,  0. ])
+    np.testing.assert_array_almost_equal(result, expected)
+
+

hands_on/pyanno_voting/pyanno/voting.py

@@ -100,3 +100,18 @@ def labels_frequency(annotations, nclasses):
         freq[k] is the frequency of elements of class k in `annotations`, i.e.
         their count over the number of total of observed (non-missing) elements
     """
+    counter = 0
+    result = np.zeros(nclasses)
+    for participant in annotations:
+        for doc in participant:
+            if doc in np.arange(nclasses):
+                result[doc] += 1
+                counter += 1
+
+    if counter != 0:
+        result = result / counter
+
+    return result
+
+
+