Method `baltic.tree.fixHangingNodes`

tree.fixHangingNodes() Method

Description

The fixHangingNodes() method in the BALTIC tree class is used to remove internal nodes that have no children. This method is crucial for maintaining a valid tree structure, especially after operations that might leave some nodes childless, such as pruning or subtree extraction.

Syntax

def fixHangingNodes(self)

Parameters

This method doesn't take any parameters.

Functionality

1. Iteratively identifies internal nodes (instances of the node class) that have no children.
2. For each identified hanging node:
   • Removes the node from its parent's list of children.
   • Removes the node from the tree's Objects list.
3. Repeats this process until no more hanging nodes are found in the tree.

Use Cases

1. Cleaning up the tree structure after pruning operations.
2. Ensuring tree validity after subtree extraction or other manipulations.
3. Preparing the tree for visualization or further analysis.
4. Removing artifacts that might have been introduced by complex tree operations.

Example

# Assuming we have a tree that might have hanging nodes

# First, let's check if we have any hanging nodes
hanging_nodes = [node for node in tree.Objects if node.is_node() and not node.children]
print(f"Number of hanging nodes before fixing: {len(hanging_nodes)}")

# Now, let's fix the hanging nodes
tree.fixHangingNodes()

# Check again for hanging nodes
hanging_nodes_after = [node for node in tree.Objects if node.is_node() and not node.children]
print(f"Number of hanging nodes after fixing: {len(hanging_nodes_after)}")

# Verify the tree structure
print(f"Total number of objects in tree: {len(tree.Objects)}")
print(f"Number of internal nodes: {len(tree.getInternal())}")
print(f"Number of leaves: {len(tree.getExternal())}")

Notes

• This method modifies the tree structure in-place. It does not return a new tree object.
• Hanging nodes can occur after operations like reduceTree(), subtree(), or manual tree manipulations.
• The method ensures that all remaining internal nodes have at least one child, maintaining a valid tree structure.
• After calling this method, you may want to update other tree properties or rerun analyses that depend on the tree structure.
• This method is often called internally by other BALTIC functions to ensure tree integrity after complex operations.
• While it's generally safe to call this method at any time, it's most useful after operations that might have altered the tree structure.
• For very large trees, this method might have a noticeable performance impact if there are many hanging nodes to remove.