# forum.alglib.net

ALGLIB forum
 It is currently Fri Sep 22, 2023 9:22 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.

 Page 1 of 1 [ 3 posts ]
 Print view Previous topic | Next topic
Author Message
 Post subject: ALGLIB, Need an help in sorting eigenvaluesPosted: Fri Aug 08, 2014 10:37 am

Joined: Fri Aug 08, 2014 10:33 am
Posts: 2
Quote:
I am using ALGLIB for calculating eigenvalues and CSML for converting double[,] var into matrix.

Code:
double[,] dataset = new VarianceAndCovariance().buildMatrix();
double[,] var = new VarianceAndCovariance().eigenvalues(dataset);
Matrix matrix = new Matrix(var);
double [] var1 = new double[1];
double [,] var2 = new double[68,2];

alglib.smatrixevd(var, 68, 1, true,out var1,out var2);

Quote:
Now this statement is returning eigenvalues(i.e. var1) in ascending order, but i want it to return in default sorting of matrix or normal mode not in ascending or descending order. How can i get eigenvalues without any sorting.
alglib.smatrixevd() function returns eigenvalues in ascending order, i want it according to the input matrix or in other words i dont want it to be sorted.
Kindly Help me i need it for my project

Top

 Post subject: Re: ALGLIB, Need an help in sorting eigenvaluesPosted: Mon Aug 11, 2014 11:03 am

Joined: Fri May 07, 2010 7:06 am
Posts: 891
Hello!

There is no such thing as "default order of eigenvalues". They are not ordered. You may rearrange then in any order, and in any case it will be eigendecomposition, i.e. one which represents matrix as A=Q*diag*Q^T. Eigensolver returns values in some order which is implementation-defined, but this order has no special meaning.

That's why values are always sorted - it is easier to work with sorted values than with unsorted ones.

Top

 Post subject: Re: ALGLIB, Need an help in sorting eigenvaluesPosted: Fri Feb 27, 2015 10:49 am

Joined: Fri Feb 27, 2015 10:40 am
Posts: 1
I posted today on google android market an app that uses most of the features available on ALGLIB (compatible with the resources available on a tablet or a smartphone). The app is called STATX and the full version is a fee (? 2). For ALGLIB Forum members is free: just send me an email and I will reply attaching the apk file (by opening the attachment with your tablet or smartphone you'll be prompted for the installation).

_________________
DdD DeViL

Top

 Display posts from previous: All posts1 day7 days2 weeks1 month3 months6 months1 year Sort by AuthorPost timeSubject AscendingDescending
 Page 1 of 1 [ 3 posts ]

 All times are UTC

#### Who is online

Users browsing this forum: No registered users and 1 guest

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

Search for:
 Jump to:  Select a forum ------------------ ALGLIB forum    ALGLIB-discuss
Powered by phpBB © 2000, 2002, 2005, 2007 phpBB Group