lib/rumale/pairwise_metric.rb in rumale-0.13.0 vs lib/rumale/pairwise_metric.rb in rumale-0.13.1

@@ -16,23 +16,36 @@
         Rumale::Validation.check_sample_array(x)
         Rumale::Validation.check_sample_array(y)
         Numo::NMath.sqrt(squared_error(x, y).abs)
       end
 
+      # Calculate the pairwise manhattan distances between x and y.
+      #
+      # @param x [Numo::DFloat] (shape: [n_samples_x, n_features])
+      # @param y [Numo::DFloat] (shape: [n_samples_y, n_features])
+      # @return [Numo::DFloat] (shape: [n_samples_x, n_samples_x] or [n_samples_x, n_samples_y] if y is given)
+      def manhattan_distance(x, y = nil)
+        y = x if y.nil?
+        Rumale::Validation.check_sample_array(x)
+        Rumale::Validation.check_sample_array(y)
+        n_samples_x = x.shape[0]
+        n_samples_y = y.shape[0]
+        distance_mat = Numo::DFloat.zeros(n_samples_x, n_samples_y)
+        n_samples_x.times do |n|
+          distance_mat[n, true] = (y - x[n, true]).abs.sum(axis: 1)
+        end
+        distance_mat
+      end
+
       # Calculate the pairwise squared errors between x and y.
       #
       # @param x [Numo::DFloat] (shape: [n_samples_x, n_features])
       # @param y [Numo::DFloat] (shape: [n_samples_y, n_features])
       # @return [Numo::DFloat] (shape: [n_samples_x, n_samples_x] or [n_samples_x, n_samples_y] if y is given)
       def squared_error(x, y = nil)
         y = x if y.nil?
         Rumale::Validation.check_sample_array(x)
         Rumale::Validation.check_sample_array(y)
-        # sum_x_vec = (x**2).sum(1)
-        # sum_y_vec = (y**2).sum(1)
-        # dot_xy_mat = x.dot(y.transpose)
-        # dot_xy_mat * -2.0 + sum_x_vec.tile(y.shape[0], 1).transpose + sum_y_vec.tile(x.shape[0], 1)
-        #
         n_features = x.shape[1]
         one_vec = Numo::DFloat.ones(n_features).expand_dims(1)
         sum_x_vec = (x**2).dot(one_vec)
         sum_y_vec = (y**2).dot(one_vec).transpose
         dot_xy_mat = x.dot(y.transpose)