Create nearestNeighbourSearch.m

Task/K-d-tree/Matlab/nearestNeighbourSearch.m

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+function [nearestPoint, nearestDist, nodesVisited] = nearestNeighbourSearch(root, queryPoint)
+    
+    nearestPoint = [];
+    nearestDist = inf;
+    nodesVisited = 0;
+
+    % Define the recursive search function
+    function search(node, depth)
+        if isempty(node)
+            return;
+        end
+
+        nodesVisited = nodesVisited + 1; 
+
+        % Calculate the current distance (squared distance)
+
+        currentPoint = node.point;      
+        currentDist = sum((queryPoint - currentPoint).^2);
+
+        % Update nearest point if the current node is closer
+
+        if isempty(nearestPoint) || currentDist < nearestDist
+            nearestPoint = currentPoint;
+            nearestDist = currentDist;
+        end
+
+        % Determine which subtree to search first (based on axis and query point)
+
+        k = length(queryPoint);    % Dimensionality of points
+        axis = mod(depth, k) + 1;
+
+        if queryPoint(axis) <= currentPoint(axis)
+            nearerSubtree = node.left;
+            furtherSubtree = node.right;
+        else
+            nearerSubtree = node.right;
+            furtherSubtree = node.left;
+        end
+
+        % Search the nearer subtree first
+
+        search(nearerSubtree, depth + 1);
+
+        % If the further subtree has a closer point
+
+        dx = queryPoint(axis) - currentPoint(axis);
+        if dx^2 < nearestDist
+            search(furtherSubtree, depth + 1);
+        end
+    end
+
+    % Search from the root of the kd-tree
+
+    search(root, 0);
+    
+end