How to do SVD without function..?

I have a Three parameters Xi,Yi,Zi.. and I am finding a SVD of them..

A=[Xi,Yi,Zi,ones(length(Xi),1)];

[U,S,V]=svd(A);

ss=diag(S);

i=find(ss==min(ss));

coeff=V(:,min(i));

coeff=coeff/norm(coeff(1:3),2);

and i am getting four parameters for plane.. the code is ok.. but,

is there any method to do SVD without using SVD function..?

[Walter Roberson]

i=find(ss==min(ss));

can be replaced with

[junk, i] = min(ss);

and you will not need to take min(i) on the next line, just i.

[Walter Roberson]

Is there a particular reason for wanting to do SVD without using the SVD function? Knowing your reason might help people select the best alternative for you.

[Lalit Patil]

SVD is almost used at many application, and one of its feature is it gives a best fit..

So, i want to know actually what real procedure happens inside SVD function so that it gives best fit..

I want to know this for my best plane fitting a*X + b*Y + c*Z + d = 0 from so many plane equations..

[Walter Roberson]

http://www.mathworks.com/company/newsletters/articles/professor-svd.html

[Lalit Patil]

This is not that thing which i want..

I want to know that what procedure happened inside SVD matlab function so that U,S,V get generated..?

Actually i want to write code for that..

[Walter Roberson]

The blog has a bunch of links.

Answer 1

[Walter Roberson]

Source code is at http://www.netlib.org/lapack/double/dgesvd.f

[Lalit Patil]

But , I can't understand what the sequence is of mathematical equations.?

I want That equations or code which can be applied insted of SVD functions..

[Walter Roberson]

That is the code that is used by MATLAB (though it is not impossible that Mathworks has tweaked the code.) Everything that is documented about exactly how MATLAB's SVD function operates is in that source code (when you include the related files for the routines it calls.)