Chapter 3 of Tom M. Mitchell. Machine Learning (free) says:
the available data has been split into three subsets: the training examples, the validation examples used for pruning the tree, and a set of test examples used to provide an unbiased estimate of accuracy over future unseen examples.
I understand this conceptually and am trying to understand this operationally.
Could someone please give an concrete example to illustrate how exactly a validation set being used for pruning a decision tree?
for example, how a exactly validation set in iris dataset for pruning a decision tree?
Note: this post is different to the one discussing how to divide dataset. this post focus on pruning.