Add stats features (#518)

* add features to stats and filterby

* add documentation

* Update views.py

* add unit tests

* response to review

docs/source/api/stats/xgi.stats.DiEdgeStat.rst

@@ -32,4 +32,6 @@
       ~DiEdgeStat.min
       ~DiEdgeStat.std
       ~DiEdgeStat.var
-      ~DiEdgeStat.moment
+      ~DiEdgeStat.moment
+      ~DiEdgeStat.argmin
+      ~DiEdgeStat.argmax

docs/source/api/stats/xgi.stats.DiNodeStat.rst

@@ -32,3 +32,5 @@
       ~DiNodeStat.std
       ~DiNodeStat.var
       ~DiNodeStat.moment
+      ~DiNodeStat.argmin
+      ~DiNodeStat.argmax

docs/source/api/stats/xgi.stats.EdgeStat.rst

@@ -32,4 +32,6 @@
       ~EdgeStat.min
       ~EdgeStat.std
       ~EdgeStat.var
-      ~EdgeStat.moment
+      ~EdgeStat.moment
+      ~EdgeStat.argmin
+      ~EdgeStat.argmax

docs/source/api/stats/xgi.stats.NodeStat.rst

@@ -31,4 +31,6 @@
       ~NodeStat.min
       ~NodeStat.std
       ~NodeStat.var
-      ~NodeStat.moment
+      ~NodeStat.moment
+      ~NodeStat.argmin
+      ~NodeStat.argmax

tests/stats/test_nodestats.py

@@ -232,6 +232,8 @@ 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.argmax() == 6
+    assert H.nodes.degree.argmin() == 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
@@ -240,6 +242,8 @@ def test_aggregates(edgelist1, edgelist2, edgelist8):
     H = xgi.Hypergraph(edgelist2)
     assert H.nodes.degree.max() == 2
     assert H.nodes.degree.min() == 1
+    assert H.nodes.degree.argmax() == 4
+    assert H.nodes.degree.argmin() == 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
@@ -248,6 +252,8 @@ def test_aggregates(edgelist1, edgelist2, edgelist8):
     H = xgi.Hypergraph(edgelist8)
     assert H.nodes.degree.max() == 6
     assert H.nodes.degree.min() == 2
+    assert H.nodes.degree.argmax() == 0
+    assert H.nodes.degree.argmin() == 5
     assert H.nodes.degree.sum() == 26
     assert round(H.nodes.degree.mean(), 3) == 3.714
     assert round(H.nodes.degree.std(), 3) == 1.385

xgi/core/views.py

@@ -254,7 +254,7 @@ def filterby(self, stat, val, mode="eq"):
         elif mode == "geq":
             bunch = [idx for idx in self if values[idx] >= val]
         elif mode == "between":
-            bunch = [node for node in self if val[0] <= values[node] <= val[1]]
+            bunch = [idx for idx in self if val[0] <= values[idx] <= val[1]]
         else:
             raise ValueError(
                 f"Unrecognized mode {mode}. mode must be one of "

xgi/stats/__init__.py

@@ -244,6 +244,34 @@ def moment(self, order=2, center=False):
         arr = self.asnumpy()
         return spmoment(arr, moment=order) if center else np.mean(arr**order)
 
+    def argmin(self):
+        """The ID corresponding to the minimum of the stat
+
+        When the minimum value is not unique, returns first
+        ID corresponding to the minimum value.
+
+        Returns
+        -------
+        hashable
+            The ID to which the minimum value corresponds.
+        """
+        d = self.asdict()
+        return min(d, key=d.get)
+
+    def argmax(self):
+        """The ID corresponding to the maximum of the stat
+
+        When the maximal value is not unique, returns first
+        ID corresponding to the maximal value.
+
+        Returns
+        -------
+        hashable
+            The ID to which the maximum value corresponds.
+        """
+        d = self.asdict()
+        return max(d, key=d.get)
+
 
 class NodeStat(IDStat):
     """An arbitrary node-quantity mapping.