amount of trees needed to work

[joachimder]

When I use this on my Random forest model it only works when I use 200 or more trees in the parameters.

n_trees = 200 forest = RandomForestRegressor(n_estimators=n_trees, random_state=42)

my optimal amount of trees is 29 but then (and not with the 200 trees) I get a warning: RuntimeWarning: invalid value encountered in true_divide g_eta_main = g_eta_raw / sum(g_eta_raw) I also can't get a confidence interval around my predicted points because of the error.

I'm a missing something, why you need such an excessive amount of trees?

Edit: minimum amount of trees needed to make it work