Hi Satraijit,

On Sun, Mar 25, 2012 at 3:02 PM, Satrajit Ghosh <[email protected]> wrote:
> hi giles,
>
> when dealing with skinny matrices  of the type few samples x lots of
> features what are the recommendations for extra trees in terms of max
> features and number of estimators?

as far as number of estimators (trees) is concerned ... the higher the better.

100 is a reasonable default but if you are in a n << p setting it may
be too low.

for max features I would suggest performing hyper parameter search:
1, 2, 4, 8, .... p

> also if a lot of the features are nuisance and most are noisy, are there any
> recommendations for feature reduction using extra trees themselves.

You could rank features by feature importance and perform recursive feature
limitation (drop at each iteration 10% of feature discarding the least
important)

Ciao
Paolo

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