From 4c5b7b2f07b3e1f661dc85828f8fee5c7c88ac72 Mon Sep 17 00:00:00 2001
From: Daniel Friesel <daniel.friesel@uos.de>
Date: Wed, 2 Mar 2022 21:40:24 +0100
Subject: CARTFunction: Add to_json method (adapted from Lennart Kaiser)

---
 lib/functions.py | 44 ++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 44 insertions(+)

(limited to 'lib')

diff --git a/lib/functions.py b/lib/functions.py
index 69788df..aeaf48e 100644
--- a/lib/functions.py
+++ b/lib/functions.py
@@ -487,6 +487,50 @@ class CARTFunction(SKLearnRegressionFunction):
     def get_max_depth(self):
         return self.regressor.get_depth()
 
+    def to_json(self, feature_names=None, **kwargs):
+        import sklearn.tree
+
+        self.leaf_id = sklearn.tree._tree.TREE_LEAF
+        self.feature_names = feature_names
+
+        ret = super().to_json(**kwargs)
+        ret.update(self.recurse_(self.regressor.tree_, 0))
+        return ret
+
+    # recursive function for all nodes:
+    def recurse_(self, tree, node_id, depth=0):
+        left_child = tree.children_left[node_id]
+        right_child = tree.children_right[node_id]
+
+        # basic leaf with standard values
+        # conversion because of numpy
+        sub_data = {
+            "functionError": None,
+            "type": "static",
+            "value": float(tree.value[node_id]),
+            "valueError": float(tree.impurity[node_id]),
+            # "samples": int(tree.n_node_samples[node_id])
+        }
+
+        # if has childs / not a leaf:
+        if left_child != self.leaf_id or right_child != self.leaf_id:
+            # sub_data["paramName"] = "X[" + str(self.regressor.tree_.feature[left_child_id]) + "]"
+            # sub_data["paramIndex"] = int(self.regressor.tree_.feature[left_child_id])
+            sub_data["paramName"] = self.feature_names[
+                self.regressor.tree_.feature[node_id]
+            ]
+            sub_data["paramDecisionValue"] = tree.threshold[node_id]
+            sub_data["type"] = "scalarSplit"
+            sub_data["child"] = {}
+
+        # child value
+        if left_child != self.leaf_id:
+            sub_data["child"]["<="] = self.recurse_(tree, left_child, depth=depth + 1)
+        if right_child != self.leaf_id:
+            sub_data["child"][">"] = self.recurse_(tree, right_child, depth=depth + 1)
+
+        return sub_data
+
 
 class LMTFunction(SKLearnRegressionFunction):
     def get_number_of_nodes(self):
-- 
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