forum.alglib.net

ALGLIB forum
It is currently Tue Sep 19, 2017 11:41 am

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  [ 4 posts ] 
Author Message
 Post subject: Questions about the w value in fisherldan function
PostPosted: Wed May 03, 2017 10:05 am 
Offline

Joined: Wed May 03, 2017 9:12 am
Posts: 2
Hello everyone.
I have some questions on the fisherldan function.

1) What are the differents between the Fisherlda function and the Fisherldan function?
2) I use two points A(3, 1.732) and B(4, 0) to test the function and the result W shows two rows of vectors and it looks like a matrix (see the attachment TestResult1). It kind of shows the gradient of the line but where is the intercept?
3) I move these two points 1 unit to the right as A(4, 1.732) and B(5, 0) and the result is the same as the above (see the attachment TestResult2). Why this happans and what should I do next?

Thanks in advance


Attachments:
TestResult2.png
TestResult2.png [ 12.18 KiB | Viewed 419 times ]
TestResult1.png
TestResult1.png [ 11.5 KiB | Viewed 419 times ]
Top
 Profile  
 
 Post subject: Re: Questions about the w value in fisherldan function
PostPosted: Wed May 03, 2017 10:35 am 
Offline
Site Admin

Joined: Fri May 07, 2010 7:06 am
Posts: 778
Hi!

Firsher LDA is not used to perform linear regression. It is used to reduce dimensionality of your data in a way which helps to linearly separate classes. First column of array W contains direction which gives best separability, second column contains direction which gives worst separability.

If you move all points in same direction, W should not change. If you rotate them - W will rotate too.


Top
 Profile  
 
 Post subject: Re: Questions about the w value in fisherldan function
PostPosted: Thu May 04, 2017 3:07 am 
Offline

Joined: Wed May 03, 2017 9:12 am
Posts: 2
Sergey.Bochkanov wrote:
Hi!

Firsher LDA is not used to perform linear regression. It is used to reduce dimensionality of your data in a way which helps to linearly separate classes. First column of array W contains direction which gives best separability, second column contains direction which gives worst separability.

If you move all points in same direction, W should not change. If you rotate them - W will rotate too.


Thank you very much! That helps a lot!

Could you please tell me the differences between the fisherlda function and the fisherldan function? According to my understanding, the fisherlda is used for one or two dimentions data and fisherldan is used for three or more, is that correct?


Top
 Profile  
 
 Post subject: Re: Questions about the w value in fisherldan function
PostPosted: Thu May 04, 2017 10:11 am 
Offline
Site Admin

Joined: Fri May 07, 2010 7:06 am
Posts: 778
fisherlda is used to get just one "most important" direction, typically in a problem with two classes (not dimensions! you can have more than two dimensions).

fisherldan returns full basis, you can pick arbitrary number of vectors from this basis.


Top
 Profile  
 
Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 4 posts ] 

All times are UTC


Who is online

Users browsing this forum: Bing [Bot] and 5 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