Fix tree pruning with NTuples

Author: tecosaur

src/DecisionTree.jl

@@ -42,10 +42,10 @@ struct Node{S, T, N}
     right   :: Union{Leaf{T, N}, Node{S, T, N}}
 end
 
-const LeafOrNode{S, T} = Union{Leaf{T}, Node{S, T}}
+const LeafOrNode{S, T, N} = Union{Leaf{T, N}, Node{S, T, N}}
 
-struct Ensemble{S, T}
-    trees :: Vector{LeafOrNode{S, T}}
+struct Ensemble{S, T, N}
+    trees :: Vector{LeafOrNode{S, T, N}}
 end
 
 Leaf(features::NTuple{T, N}) where {T, N} =

src/classification/main.jl

@@ -113,27 +113,25 @@ function prune_tree(tree::LeafOrNode{S, T}, purity_thresh=1.0) where {S, T}
     if purity_thresh >= 1.0
         return tree
     end
-    function _prune_run(tree::LeafOrNode{S, T}, purity_thresh::Real) where {S, T}
-        N = length(tree)
-        if N == 1        ## a Leaf
+    function _prune_run(tree::LeafOrNode{S, T, N}, purity_thresh::Real) where {S, T, N}
+        L = length(tree)
+        if L == 1        ## a Leaf
             return tree
-        elseif N == 2    ## a stump
-            all_labels = [tree.left.values; tree.right.values]
-            majority = majority_vote(all_labels)
-            matches = findall(all_labels .== majority)
-            purity = length(matches) / length(all_labels)
+        elseif L == 2    ## a stump
+            combined = tree.left.values .+ tree.right.values
+            total = tree.left.total + tree.right.total
+            majority = argmax(combined)
+            purity = combined[majority] / total
             if purity >= purity_thresh
-                features = Tuple(unique(all_labels))
-                featfreq = Tuple(sum(all_labels .== f) for f in features)
-                return Leaf{T}(features, argmax(featfreq),
-                               featfreq, length(all_labels))
+                return Leaf{T, N}(tree.left.features, majority, combined, total)
             else
                 return tree
             end
         else
-            return Node{S, T}(tree.featid, tree.featval,
-                        _prune_run(tree.left, purity_thresh),
-                        _prune_run(tree.right, purity_thresh))
+            return Node{S, T, N}(
+                tree.featid, tree.featval,
+                _prune_run(tree.left, purity_thresh),
+                _prune_run(tree.right, purity_thresh))
         end
     end
     pruned = _prune_run(tree, purity_thresh)