Hi,

Author here. Thanks for the links. I originally planned to try a bigger dataset but didn't want to make the article too long, so left out the optimizations.

I had to do the same exercise for my ML class and had similar results. Random pruning (mostly) worked great for me.

IMHO, While DTs do overfit a lot, they are a great starting point for beginners because of their (relative) simplicity. Better to start light and then introduce the math heavy neural nets and SVMs.