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I read some material:

However I can find if I change feature order(the set of feature name: [a,b,c] change into [b,a,c]) in the data. Does this actually affect decision tree result?

Rachel Jennifer
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Not really. Sklearn generally uses Cart trees where the best split is decided by picking the feature that minimizes a cost function. So the order of column doesn't really matter.

Giovanni Bruner
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  • Thank you, I have a question. If the data is so large(Maybe [10^6, 10^5]). In the first time, I have to compute all the feature's best splitter. That maybe O(n^2). This is very slowly. Is this correct? – Rachel Jennifer May 12 '17 at 15:39
  • Yes, a single CART decision tree will need to scan trough all the data and all the features to find the best split. Usually you wouldn’t code a tree yourself, since there are many optimised libraries that do that job for you pretty quickly. – Giovanni Bruner May 13 '17 at 18:07