From the course: Machine Learning and AI Foundations: Decision Trees with SPSS

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Understanding pruning

Understanding pruning

From the course: Machine Learning and AI Foundations: Decision Trees with SPSS

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Understanding pruning

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- [Narrator] We're going to talk about an aspect of Cart that's truly fundamental to how it works. I'm going to open the CHAID and CART stream. And we're going to talk about pruning. So, first, I'm going to remind you what our Cart model looked like. Here it is. I'm going to zoom out one click. And, that's the whole tree. So we can see that it has two levels and four leaf nodes. And, the cart algorithm deselect prune tree to avoid over fitting. And, that might sound a bit ominous. It really needs to be because pruning is a pretty serious thing, as we're going to see. It's going to have a big impact on the tree. We're going to run that. Here we are. I'm going to zoom out a bit so that you can see. But I have to zoom out some more and it keeps going. That's still not the entire tree. That's almost the whole tree, but, obviously, it's had a really dramatic impact. So, what is it doing? What is pruning? Well it's full name is cost complexity pruning. Starting from the bottom of the tree…

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