initial import of material for public archive into git

We're creating a fresh archive because the history for our old chapter includes
API keys, data files, and other material we can't share.

code/data_processing/make_network.py

@@ -0,0 +1,26 @@
+'''Takes a CSV of retrieved articles, and creates an igraph
+network from them (not even close to done)'''
+
+class CitationNetwork(igraph.Graph):
+    def __init__(self, network_type):
+        super().__init__(directed=True)
+        self.temp_edges = []
+        self.temp_vertices = []
+        self.network_type = network_type
+
+    def add_vertices(self, to_node, from_nodes):
+        self.temp_vertices += [[from_node, to_node] for from_node in from_nodes]
+
+    def make_network(self):
+        # Get the unique set of nodes, and add them.
+        nodes = set([v for v in self.temp_vertices if v['eid'] not in self.vs['name']])
+        nodes = sorted(nodes)
+        self.add_vertices(nodes)
+        self.add_edges(self.temp_edges)
+        self.es['weight'] = 1
+
+    def collapse_weights(self):
+        self.simplify(combine_edges={"weight": "sum"})
+
+    def add_citations(eid, citations):
+        self.retrieved_eids.append(eid)