Add tree learners to strategy evaluation directory

strategy_evaluation/RTLearner.py

@@ -0,0 +1,30 @@
+import numpy as np
+from AbstractTreeLearner import AbstractTreeLearner
+
+
+class RTLearner(AbstractTreeLearner):
+
+    def __init__(self, leaf_size = 1, verbose = False):
+        self.leaf_size = leaf_size
+        self.verbose = verbose
+
+    def get_i_and_split_value(self, xs, y):
+        """
+        @summary: Pick a random i and split value.
+
+        Make sure that not all X are the same for i and also pick
+        different values to average the split_value from.
+        """
+        i = np.random.randint(0, xs.shape[1])
+        while np.all(xs[0,i] == xs[:,i]):
+            i = np.random.randint(0, xs.shape[1])
+
+        # I don't know about the performance of this, but at least it
+        # terminates reliably. If the two elements are the same something is
+        # wrong.
+        a = np.array(list(set(xs[:, i])))
+        r1, r2 = np.random.choice(a, size = 2, replace = False)
+        assert(r1 != r2)
+        split_value = (r1 + r2) / 2.0
+        return i, split_value
+