LU Factorization by Doolittle's method

LU factorization of a square matrix.

Description

This program factorize(decompose)the square matrix of any size into a product of a Lower-triangular matrix (L) and an Upper-triangular matrix (U). All the elements of the main diagonal in the L matrix are ones, (Doolittle's method).

This factorization is very helpfull in solving different mathematical problems and problems in linear control systems.

• MATLAB release: MATLAB 7 (R14)

[Duane Hanselman]

1) This is a script file, not a function.
2) Why use this function over the builtin MATLAB function LU?
3) Many For Loops in the script are not needed, e.g., you can start L with L=eye(m); rather than with a For Loop that does the same thing.
4) Does your code implement pivoting?
5) Nice homework solution for a beginning numerical methods class.

[Joseph Peter]

Good For implenting Doolittle's method (the elements of the main diagonal are ones).

[John Michael]

Good, as showing the basics of decomposition

[Hasan Ali]

 

[Dani Patrick]

 

[Alex Roberto]

 

[Camilo Ardila]

 

[Duane Hanselman]

Not a function. Clears the base workspace without warning! Poorly duplicates what the function LU does in MATLAB.

[masoume azarpour]

 

[John D'Errico]

Why use a script that does an LU factorization in a completely unvectorized fashion? Especially when there is already a far faster implementation of an LU in matlab itself? Beware, this clears your workspace, then makes you type in the matrix. Its just the author's homework assignment.

[Andres Fernandez]

It seems written for visual basic, it doesn't use the Matrix Algebra MatLAB offers at all.

[Ahmad Warsy]

i need this method to finish my thesis about dispatching

[John Lee]

This is an excellent program to explain the LU decomposition.

[amir khan]

very good

[Tim Davis]

The file doesn't have any comments, so it isn't useful as an educational tool. The lutx.m function in Cleve Moler's NCM toolbox (http://www.mathworks.com/moler/ncmfilelist.html) is much better code (simpler, easier to read, and well commented). Plus, lutx.m comes with extensive documentation in Cleve's book which you can download for free. The file here has none of that.

Cleve even has an LU GUI in which you can watch the LU factorization, with pivoting, occur before your very eyes.

So for educational use, there are far far better alternatives.

Of course, for dense or sparse LU factorization this function (if it were converted into a function) would not be used in production code since it's far far slower
than the MATLAB built-in LU.

So why is it here? What purpose could it serve? Why does the File Exchange have a plethora of Gaussian Elimination variants such as this one?

I would kindly suggest that this file be withdrawn.

[Muhammad Fahim]

Nice

[Tim Davis]

See my comments below - I didn't select a rating in my last review.

[Lara Evans]

It was usefull for me.

[noppanun suksomboon]

 

[Peter Androv]

Thanks, Excellent.

[Husam Aldahiyat]

No comments, messes workspace, C style programming. This file should be removed from the FEX.

[abdullah alzkarneh]

thx Dr.yaseen you are creative I hope many successes to you