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prune

Produce sequence of classification subtrees by pruning

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Syntax

tree1 = prune(tree)
tree1 = prune(tree,Name,Value)

Description

tree1 = prune(tree) creates a copy of the classification tree tree with its optimal pruning sequence filled in.

example

tree1 = prune(tree,Name,Value) creates a pruned tree with additional options specified by a Name,Value pair argument. You can only use one option at a time.

Examples

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Open Live Script

Construct and display a full classification tree for Fisher's iris data.

load fisheriris;
varnames = {'SL','SW','PL','PW'};
t1 = fitctree(meas,species,'MinParentSize',5,'PredictorNames',varnames);
view(t1,'Mode','graph');

Figure Classification tree viewer contains an axes object and other objects of type uimenu, uicontrol. The axes object contains 21 objects of type line, text. One or more of the lines displays its values using only markers

Construct and display the next largest tree from the optimal pruning sequence.

t2 = prune(t1,'Level',1);
view(t2,'Mode','graph');

Figure Classification tree viewer contains an axes object and other objects of type uimenu, uicontrol. The axes object contains 15 objects of type line, text. One or more of the lines displays its values using only markers

Input Arguments

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Classification tree, specified as a ClassificationTree model object produced by the fitctree function.

Name-Value Arguments

Specify optional pairs of arguments as Name1=Value1,...,NameN=ValueN, where Name is the argument name and Value is the corresponding value. Name-value arguments must appear after other arguments, but the order of the pairs does not matter.

Before R2021a, use commas to separate each name and value, and enclose Name in quotes.

Example: tree1 = prune(tree,'Level',1)

Pruning cost, specified as a numeric scalar. When this option is specified, prune prunes tree to the specified value of the pruning cost.

Pruning level, specified as a numeric scalar from 0 (no pruning) to the largest pruning level of this tree max(tree.PruneList).

Branch nodes to turn into leaf nodes, specified as a numeric vector with elements from 1 to tree.NumNodes. Any tree branch nodes listed in Nodes become leaf nodes in tree1, unless their parent nodes are also pruned.

Tips

tree1 = prune(tree) returns the decision tree tree1 that is the full, unpruned tree, but with optimal pruning information added. This is useful only if you created tree by pruning another tree, or by using the fitctree function with pruning set 'off'. If you plan to prune a tree multiple times along the optimal pruning sequence, it is more efficient to create the optimal pruning sequence first.

Extended Capabilities

Version History

Introduced in R2011a

See Also