Added recipe

docs/source/api/recipes/recipes.ipynb

@@ -835,6 +835,73 @@
     "matching_ids = [k for k, v in H.degree().items() if v == d]\n",
     "print(f\"Nodes {', '.join(matching_ids)} have degree {d}\")"
    ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "## 18. Define a custom filtering function\n",
+    "\n",
+    "In addition to the pre-defined filtering functionality, one can also define a custom comparison operator to compare statistics and attributes.\n",
+    "\n",
+    "First, we show an example for numerical statistics and second, an example for attributes."
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "**Numerical statistics**"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "import xgi\n",
+    "\n",
+    "outsiderange = lambda val, arg: arg[0] >= val or val >= arg[1]\n",
+    "\n",
+    "H = xgi.load_xgi_data(\"email-enron\")\n",
+    "print(H.num_nodes)\n",
+    "\n",
+    "# Get all of the dates\n",
+    "nodes = H.nodes.filterby(\"degree\", [3, 20], mode=outsiderange)\n",
+    "print(len(nodes))"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "**Attributes**"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "import datetime\n",
+    "\n",
+    "import xgi\n",
+    "\n",
+    "date1 = datetime.datetime(2000, 1, 1)\n",
+    "date2 = datetime.datetime(2001, 1, 1)\n",
+    "datecompare = (\n",
+    "    lambda date, arg: arg[0] <= datetime.datetime.fromisoformat(date) <= arg[1]\n",
+    ")\n",
+    "\n",
+    "H = xgi.load_xgi_data(\"email-enron\")\n",
+    "print(H.num_edges)\n",
+    "\n",
+    "# Get all of the dates\n",
+    "e = H.edges.filterby_attr(\"timestamp\", [date1, date2], mode=datecompare)\n",
+    "print(len(e))"
+   ]
   }
  ],
  "metadata": {