# Matrix class for ruby? **URL:** \ **Category:** Ruby\ **Created:** [December 21, 2006, 1:42pm UTC](https://www.ruby-forum.com/t/matrix-class-for-ruby/80114 "2006-12-21T13:42:20Z")\ **Posts on this page:** 5\ **Page:** 1
**Author:** ![seepee](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/s/bbe5ce/32.png) [@seepee](https://www.ruby-forum.com/u/seepee)\ **Post date:** [December 21, 2006, 1:42pm UTC](https://www.ruby-forum.com/t/matrix-class-for-ruby/80114/1 "2006-12-21T13:42:20Z")
Does anyone know of a functional Matrix math class for ruby that could multiply, add and substract 3x2 or larger matrices. The matrix.rb that is in Ruby API cannot multiply anything larger than 2x2 matrices, which makes it useless for 2D or 3D graphics (for instance). SP ---
**Author:** ![seepee](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/s/bbe5ce/32.png) [@seepee](https://www.ruby-forum.com/u/seepee)\ **Post date:** [December 21, 2006, 1:50pm UTC](https://www.ruby-forum.com/t/matrix-class-for-ruby/80114/2 "2006-12-21T13:50:22Z")
On 12/21/06, seepee [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) wrote: > Does anyone know of a functional Matrix math class for ruby that could > multiply, add and substract 3x2 or larger matrices. > > The matrix.rb that is in Ruby API cannot multiply anything larger than 2x2 > matrices, which makes it useless for 2D or 3D graphics (for instance). Are you sure? $ irb irb(main):001:0\> Matrix[[1,2,3],[1,2,3],[1,2,3]] \* Matrix[[1,2,3],[1,2,3],[1,2,3]] =\> Matrix[[6, 12, 18], [6, 12, 18], [6, 12, 18]] irb(main):002:0\> VERSION =\> 1.8.4 $ ---
**Author:** ![seepee](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/s/bbe5ce/32.png) [@seepee](https://www.ruby-forum.com/u/seepee)\ **Post date:** [December 21, 2006, 2:26pm UTC](https://www.ruby-forum.com/t/matrix-class-for-ruby/80114/3 "2006-12-21T14:26:24Z")
seepee wrote: > Does anyone know of a functional Matrix math class for ruby that could > multiply, add and substract 3x2 or larger matrices. > > The matrix.rb that is in Ruby API cannot multiply anything larger than 2x2 > matrices, which makes it useless for 2D or 3D graphics (for instance). OK, I understand now: you want graphical transformations. They are _not_ real matrices, but the combination of a real matrix and a translation vector. So you need special rules to combine them (although for additions and substractions, standard matrix multiplications should work). I don’t know any package doing that in Ruby – but if you consider writing one, that would definitely be an interesting addition. Cheers ! ``` Vince ``` ---
**Author:** ![seepee](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/s/bbe5ce/32.png) [@seepee](https://www.ruby-forum.com/u/seepee)\ **Post date:** [December 21, 2006, 4:30pm UTC](https://www.ruby-forum.com/t/matrix-class-for-ruby/80114/4 "2006-12-21T16:30:35Z")
On Dec 21, 2006, at 6:24 AM, Vincent F. wrote: > translation vector. So you need special rules to combine them (although > for additions and substractions, standard matrix multiplications should > work). I don’t know any package doing that in Ruby – but if you > consider writing one, that would definitely be an interesting addition. An RST matrix has an implicit 0 0 0 1 row along the bottom. Nothing more complicated than that. Actually when dealing with projection matrices, this ‘implicit’ bottom row gets used to define the perspective value of the camera. That said, matrix.rb is very shoddy - it’s missing several important vector operations (like, oh, -Vector and Vector/Numeric), and it uses Vector_Matrix instead of the correct Matrix_Vector. Dan ---
**Author:** ![seepee](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/s/bbe5ce/32.png) [@seepee](https://www.ruby-forum.com/u/seepee)\ **Post date:** [December 21, 2006, 4:54pm UTC](https://www.ruby-forum.com/t/matrix-class-for-ruby/80114/5 "2006-12-21T16:54:39Z")
Dan Uznanski wrote: > > > > Actually when dealing with projection matrices, this ‘implicit’ bottom > row gets used to define the perspective value of the camera. > > That said, matrix.rb is very shoddy - it’s missing several important > vector operations (like, oh, -Vector and Vector/Numeric), and it uses > Vector_Matrix instead of the correct Matrix_Vector. > > Dan I wouldn’t call it “shoddy”. My biggest complaint with Matrix is that a Matrix is immutable – if you want to set elements, you have to do so in an Array and then create a new Matrix from the Array. The whole rational / complex / matrix / mathn collection looks to me like an attempt to provide “high-school algebra” constructs in Ruby that work the way you’d expect them to work. For example, you can get the _exact_ inverse of a non-singular matrix with rational elements, and I suppose, though I haven’t tried it, the same thing for a non-singular matrix with complex rational elements. For _small_ one-off calculations and calculations where high speed isn’t required, they do just that. However, if what you want to do is, say, lots of graphical transformations at high speed using floating point arithmetic, like you might in a video game, you want NArray. – M. Edward (Ed) Borasky, FBG, AB, PTA, PGS, MS, MNLP, NST, ACMC(P) [http://borasky-research.blogspot.com/](http://borasky-research.blogspot.com/) If God had meant for carrots to be eaten cooked, He would have given rabbits fire.