added sum as a stats method

tests/stats/test_edgestats.py

@@ -51,20 +51,23 @@ def test_aggregates(edgelist1, edgelist2, edgelist8):
     H = xgi.Hypergraph(edgelist1)
     assert H.edges.order.max() == 2
     assert H.edges.order.min() == 0
+    assert H.edges.order.sum() == 5
     assert round(H.edges.order.mean(), 3) == 1.25
     assert round(H.edges.order.std(), 3) == 0.829
     assert round(H.edges.order.var(), 3) == 0.688
 
     H = xgi.Hypergraph(edgelist2)
     assert H.edges.order.max() == 2
     assert H.edges.order.min() == 1
+    assert H.edges.order.sum() == 4
     assert round(H.edges.order.mean(), 3) == 1.333
     assert round(H.edges.order.std(), 3) == 0.471
     assert round(H.edges.order.var(), 3) == 0.222
 
     H = xgi.Hypergraph(edgelist8)
     assert H.edges.order.max() == 4
     assert H.edges.order.min() == 1
+    assert H.edges.order.sum() == 17
     assert round(H.edges.order.mean(), 3) == 1.889
     assert round(H.edges.order.std(), 3) == 0.875
     assert round(H.edges.order.var(), 3) == 0.765

tests/stats/test_nodestats.py

@@ -160,20 +160,23 @@ def test_aggregates(edgelist1, edgelist2, edgelist8):
     H = xgi.Hypergraph(edgelist1)
     assert H.nodes.degree.max() == 2
     assert H.nodes.degree.min() == 1
+    assert H.nodes.degree.sum() == 9
     assert round(H.nodes.degree.mean(), 3) == 1.125
     assert round(H.nodes.degree.std(), 3) == 0.331
     assert round(H.nodes.degree.var(), 3) == 0.109
 
     H = xgi.Hypergraph(edgelist2)
     assert H.nodes.degree.max() == 2
     assert H.nodes.degree.min() == 1
+    assert H.nodes.degree.sum() == 7
     assert round(H.nodes.degree.mean(), 3) == 1.167
     assert round(H.nodes.degree.std(), 3) == 0.373
     assert round(H.nodes.degree.var(), 3) == 0.139
 
     H = xgi.Hypergraph(edgelist8)
     assert H.nodes.degree.max() == 6
     assert H.nodes.degree.min() == 2
+    assert H.nodes.degree.sum() == 26
     assert round(H.nodes.degree.mean(), 3) == 3.714
     assert round(H.nodes.degree.std(), 3) == 1.385
     assert round(H.nodes.degree.var(), 3) == 1.918

xgi/readwrite/xgi_data.py

@@ -34,7 +34,7 @@ def load_xgi_data(dataset, nodetype=None, edgetype=None):
     index = requests.get(index_url).json()
     if dataset not in index:
         print("Valid dataset names:")
-        print(*index, sep = "\n")
+        print(*index, sep="\n")
         raise XGIError("Must choose a valid dataset name!")
 
     r = requests.get(index[dataset]["url"])

xgi/stats/__init__.py

@@ -231,6 +231,10 @@ def min(self):
         """The minimum value of this stat."""
         return self.asnumpy().min(axis=0)
 
+    def sum(self):
+        """The sum of this stat."""
+        return self.asnumpy().sum(axis=0)
+
     def mean(self):
         """The arithmetic mean of this stat."""
         return self.asnumpy().mean(axis=0)