Question

If we do not define number of trees to be built in random forest then how many treesrandom forest internally creates

Answer 1

Answer:

You should use as many trees as you can. There is no performance penalty for having more trees, it just takes longer. The conventional wisdom is to look at the out of bag error rate as more trees are grown and stop once it "levels out". This is OK if you are only interested in prediction. If you want to extract variable importance you should include more trees because the permutation variable importance measures take longer to settle down.

____✔

Answer 2

As there is so much chlorine in an active form at the end of the polar night (September in Antarctica) the ozone hole can grow to a size larger than the United States. At the South Pole, ozone levels below 100 Dobson Units are now frequently observed in late September and early October.

__________________❣