Merge pull request #61 from tlapusan/leaf_samples_distribution

Leaf samples distribution

dtreeviz/shadow.py

@@ -230,19 +230,28 @@ def get_node_type(_tree_model):
         return node_type
 
     @staticmethod
-    def get_leaf_sample_counts(_tree_model):
+    def get_leaf_sample_counts(_tree_model, min_samples=0, max_samples=None):
         """Get the number of samples for each leaf.
 
+        There is the option to filter the leaves with less than min_samples or more than max_samples.
+
+        :param min_samples: int
+            Min number of samples for a leaf
+        :param max_samples: int
+            Max number of samples for a leaf
+
         :return: tuple
-            Contains a list of leaf ids and a list of leaf samples
+            Contains a numpy array of leaf ids and an array of leaf samples
         """
 
         node_type = ShadowDecTree.get_node_type(_tree_model)
         n_node_samples = _tree_model.tree_.n_node_samples
 
-        leaf_samples = [(i, n_node_samples[i]) for i in range(0, _tree_model.tree_.node_count) if node_type[i]]
+        max_samples = max_samples if max_samples else n_node_samples.max()
+        leaf_samples = [(i, n_node_samples[i]) for i in range(0, _tree_model.tree_.node_count) if node_type[i]
+                        and min_samples <= n_node_samples[i] <= max_samples]
         x, y = zip(*leaf_samples)
-        return x, y
+        return np.array(x), np.array(y)
 
     @staticmethod
     def get_leaf_sample_counts_by_class(_tree_model):

dtreeviz/trees.py

@@ -1257,12 +1257,20 @@ def viz_leaf_samples(tree_model: (tree.DecisionTreeRegressor, tree.DecisionTreeC
                      colors: dict = None,
                      fontsize: int = 14,
                      fontname: str = "Arial",
-                     grid: bool = False):
+                     grid: bool = False,
+                     bins: int = 10,
+                     min_samples: int = 0,
+                     max_samples: int = None):
     """Visualize the number of training samples from each leaf.
 
+    There is the option to filter the leaves with less than min_samples or more than max_samples. This is helpful
+    especially when you want to investigate leaves with number of samples from a specific range.
+
     If display_type = 'plot' it will show leaf samples using a plot.
     If display_type = 'text' it will show leaf samples as plain text. This method is preferred if number
     of leaves is very large and the plot become very big and hard to interpret.
+    If display_type = 'hist' it will show leaf sample histogram. Useful when you want to easily see the general
+    distribution of leaf samples.
 
     :param tree_model: sklearn.tree
         The tree to interpret
@@ -1278,9 +1286,15 @@ def viz_leaf_samples(tree_model: (tree.DecisionTreeRegressor, tree.DecisionTreeC
         Plot labels font name
     :param grid: bool
         Whether to show the grid lines
+    :param bins: int
+        Number of histogram bins
+    :param min_samples: int
+        Min number of samples for a leaf
+    :param max_samples: int
+        Max number of samples for a leaf
     """
 
-    leaf_id, leaf_samples = ShadowDecTree.get_leaf_sample_counts(tree_model)
+    leaf_id, leaf_samples = ShadowDecTree.get_leaf_sample_counts(tree_model, min_samples, max_samples)
 
     if display_type == "plot":
         colors = adjust_colors(colors)
@@ -1303,6 +1317,21 @@ def viz_leaf_samples(tree_model: (tree.DecisionTreeRegressor, tree.DecisionTreeC
     elif display_type == "text":
         for leaf, samples in zip(leaf_id, leaf_samples):
             print(f"leaf {leaf} has {samples} samples")
+    elif display_type == "hist":
+        colors = adjust_colors(colors)
+
+        fig, ax = plt.subplots(figsize=figsize)
+        ax.spines['top'].set_visible(False)
+        ax.spines['right'].set_visible(False)
+        ax.spines['left'].set_linewidth(.3)
+        ax.spines['bottom'].set_linewidth(.3)
+        n, bins, patches = ax.hist(leaf_samples, bins=bins, color=colors["hist_bar"])
+        for rect in patches:
+            rect.set_linewidth(.5)
+            rect.set_edgecolor(colors['rect_edge'])
+        ax.set_xlabel("leaf sample", fontsize=fontsize, fontname=fontname, color=colors['axis_label'])
+        ax.set_ylabel("leaf count", fontsize=fontsize, fontname=fontname, color=colors['axis_label'])
+        ax.grid(b=grid)
 
 
 def ctreeviz_leaf_samples(tree_model: (tree.DecisionTreeClassifier),