forum.alglib.net

ALGLIB forum
It is currently Sun Dec 22, 2024 6:31 pm

All times are UTC


Forum rules


1. This forum can be used for discussion of both ALGLIB-related and general numerical analysis questions
2. This forum is English-only - postings in other languages will be removed.



Post new topic Reply to topic  [ 2 posts ] 
Author Message
 Post subject: decisionforest missclassification
PostPosted: Tue Oct 28, 2014 7:39 am 
Offline

Joined: Tue Oct 28, 2014 7:31 am
Posts: 1
hello,
i use decision-forest for a 2 class classification and when building a forest it says that miss-classification is about .02 in final report. but when i try to process each training data with process function the probabilities return to me is highly biased to class 0 (avg .95) and class 1 is rare (avg .05). is it possible i train the forest incorrectly or use process function incorrect?
is there any samples to see how to make and use decision-forest from a double array of size 10000 instances?
i train data with a real_2d array with columns nfeature+1 and test data with real_1d array with columns nfeature.
thanks in advance


Top
 Profile  
 
 Post subject: Re: decisionforest missclassification
PostPosted: Wed Oct 29, 2014 9:36 am 
Offline
Site Admin

Joined: Fri May 07, 2010 7:06 am
Posts: 927
Is it possible that class 1 is really rare in your training set and can not be easily separated from class 0? When two classes can not be separated, decision forest returns expected class membership probabilities. Say, if one sample of class 1 is closely surrounded by 20 samples of class 0, then forest will return probability equal to ~0.05.


Top
 Profile  
 
Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 2 posts ] 

All times are UTC


Who is online

Users browsing this forum: No registered users and 39 guests


You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot post attachments in this forum

Search for:
Jump to:  
cron
Powered by phpBB © 2000, 2002, 2005, 2007 phpBB Group