https://github.com/erosb/matrix-operations

matrix operations
https://github.com/erosb/matrix-operations

Last synced: 21 days ago
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matrix operations

• Host: GitHub
• URL: https://github.com/erosb/matrix-operations
• Owner: erosb
• License: bsd-2-clause
• Created: 2012-05-21T10:49:05.000Z (over 12 years ago)
• Default Branch: master
• Last Pushed: 2012-05-21T15:34:24.000Z (over 12 years ago)
• Last Synced: 2024-10-18T10:07:53.988Z (about 1 month ago)
• Language: Java
• Size: 109 KB
• Stars: 0
• Watchers: 3
• Forks: 0
• Open Issues: 0
• Metadata Files:
  • Readme: README.md
  • License: LICENSE.md

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README

        
Matrix Operations

=================

This project is intended to serve as an example of implementing some basic matrix-related

computations in Java. Originally it was my homework in subject "numerical analysis" at

University of Debrecen. Later I decided to make it public since some people asked me to

give some examples on Java programming. I hope the code quality is fairly good, although

it contains some duplications and some dead code too. Recently I worked on the API docs,

but it really needs further improvements, especially the "expansion by minors" determinant

computation alorithm.

The software can perform the following operations:

* calculate the inverse of a given matrix

* calculate the determinant of a given matrix

* calculate the condition number of a given matrix

	

Although this project is used as a kind of example on Java programming in general sadly

it is math-related (to be honest I really hate math). I learned the underlying theory

from the ebook titled "Diszkrét matematika II" written by Sándor Bácsó at the University

of Debrecen, but the following resources are also easy to understand (and available in

English):

	

* matrix inversion: http://www.purplemath.com/modules/mtrxinvr.htm

* matrix determinant calculation:

	- the Rule of Sarrus for 2x2 and 3x3 matrices: http://en.wikipedia.org/wiki/Rule_of_Sarrus

	- matrix expansion by minors for bigger matrices: http://www.intmath.com/matrices-determinants/1-determinants.php

* matrix condition number: http://en.wikipedia.org/wiki/Condition_number#Matrices

	

Brief guidelines for examining the code

---------------------------------------

The inverse and condition number calculations are fairly straightforward, the matrix.Main

class methods read the matrices from the standard input ("command line") then the actual

calculations are done by the getInverted() and getCondition() methods.To be honest I didn't

spend too much time on implementing these, therefore both uses cloning of the initial matrices,

probably some less memory consumptive implementations are also possible.

The determinant calculation is a bit more complex. If you want to calculate the determinant

of a matrix then first you have to get a DeterminantProcessor instance using

DeterminantProcessorFactory.getDeterminantProcessor() . This will return the DeterminantProcessor

instance which seems to be the best for the given matrix. In the cases of 2x2 and 3x3

matrices a DeterminantProcessorSarus instance will be returned, otherwise a

DeterminantProcessorExpansion instace. The first one is still trivial, since the rule of

Sarrus is very simple to implement in any programming languages. The expansion by minors

algorithm is a more complex topic.

Misc

----

* unittests may be useful for understanding

* the software can be used as a class library too - but I'm fairly sure some much

		better quality java libs are available for these tasks.