# 2dim array/matrix **URL:** \ **Category:** Ruby\ **Created:** [November 28, 2005, 1:23pm UTC](https://www.ruby-forum.com/t/2dim-array-matrix/48995 "2005-11-28T13:23:38Z")\ **Posts on this page:** 8\ **Page:** 1
**Author:** ![wollez](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/w/58f4c7/32.png) [@wollez](https://www.ruby-forum.com/u/wollez)\ **Post date:** [November 28, 2005, 1:23pm UTC](https://www.ruby-forum.com/t/2dim-array-matrix/48995/1 "2005-11-28T13:23:38Z")
hello, I’m quite new to programming as well to ruby. I want to store data in a 2 dimensional array. How can I do this? A more detailed describtion of what I want to do: I have data from a digital elevation model. This is stored in a log txt file. I want to read it in and store it in an array or matrix. Because there are some error/gaps in the data I want to check for these values and calculate an average from the surrounding values. At the end all values should get written to an other txt file as x, y, z triples. The main problem for me to start is the 2dimensional storage. I know the needed size of the 2dim array/matrix (x-dim,y-dim). For getting the data in I was thinking of something like: dem[xi][yi]=value . Kind regards Wolfgang ---
**Author:** ![wollez](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/w/58f4c7/32.png) [@wollez](https://www.ruby-forum.com/u/wollez)\ **Post date:** [November 28, 2005, 1:56pm UTC](https://www.ruby-forum.com/t/2dim-array-matrix/48995/2 "2005-11-28T13:56:03Z")
Wolfgang wrote: > the end all values should get written to an other txt file as x, y, z > triples. The main problem for me to start is the 2dimensional > storage. I know the needed size of the 2dim array/matrix > (x-dim,y-dim). For getting the data in I was thinking of something > like: dem[xi][yi]=value . The easiest to achieve that is matrix = Array.new(dim\_x) { Array.new(dim\_y) } There are also some matrix classes on the RAA [http://raa.ruby-lang.org/search.rhtml?search=matrix](http://raa.ruby-lang.org/search.rhtml?search=matrix) For storage you can use CSV implementations or cook your own: File.open(“matrix.csv”, “w”) do |io| matrix.each\_with\_index do |yvalues, xidx| yvalues.each\_with\_index do |val, yidx| io.print xidx,yidx,val,“\n” end end end etc. HTH Kind regards ``` robert ``` ---
**Author:** ![wollez](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/w/58f4c7/32.png) [@wollez](https://www.ruby-forum.com/u/wollez)\ **Post date:** [November 28, 2005, 2:04pm UTC](https://www.ruby-forum.com/t/2dim-array-matrix/48995/3 "2005-11-28T14:04:12Z")
Wolfgang wrote: > values should get written to an other txt file as x, y, z triples. The > main problem for me to start is the 2dimensional storage. I know the > needed size of the 2dim array/matrix (x-dim,y-dim). For getting the data > in I was thinking of something like: dem[xi][yi]=value . > > Kind regards > > Wolfgang Ruby has a Matrix class in the standard library. Check out “matrix” in the [RDoc Documentation](http://www.ruby-doc.org/stdlib/). ---
**Author:** ![wollez](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/w/58f4c7/32.png) [@wollez](https://www.ruby-forum.com/u/wollez)\ **Post date:** [November 28, 2005, 2:52pm UTC](https://www.ruby-forum.com/t/2dim-array-matrix/48995/4 "2005-11-28T14:52:44Z")
On 28/11/05, Wolfgang [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) wrote: > this works but when I try: > m.=123 > puts m > I only get an error. > > Wolfgang Try these: puts m[1,1] m[1,1] = 123 pits m[1,1] brian – [http://ruby.brian-schroeder.de/](http://ruby.brian-schroeder.de/) Stringed instrument chords: [http://chordlist.brian-schroeder.de/](http://chordlist.brian-schroeder.de/) ---
**Author:** ![wollez](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/w/58f4c7/32.png) [@wollez](https://www.ruby-forum.com/u/wollez)\ **Post date:** [November 28, 2005, 2:52pm UTC](https://www.ruby-forum.com/t/2dim-array-matrix/48995/5 "2005-11-28T14:52:45Z")
Wolfgang wrote: > this works but when I try: > m.=123 > puts m > I only get an error. You probably misread the documentation. Did you try m[1,1] m[1,1] = 123 ? Kind regards ``` robert ``` ---
**Author:** ![wollez](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/w/58f4c7/32.png) [@wollez](https://www.ruby-forum.com/u/wollez)\ **Post date:** [November 28, 2005, 3:04pm UTC](https://www.ruby-forum.com/t/2dim-array-matrix/48995/6 "2005-11-28T15:04:52Z")
> > > > > “R” == Robert K. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) writes: R\> m[1,1] = 123 Try it 🙂 moulon% ruby -rmatrix -e ‘m = Matrix[[25, 93], [-1, 66]]; m[1, 1] = 123’ -e:1: undefined method `[]=’ for Matrix[[25, 93], [-1, 66]]:Matrix (NoMethodError) moulon% Guy Decoux ---
**Author:** ![wollez](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/w/58f4c7/32.png) [@wollez](https://www.ruby-forum.com/u/wollez)\ **Post date:** [November 28, 2005, 4:05pm UTC](https://www.ruby-forum.com/t/2dim-array-matrix/48995/7 "2005-11-28T16:05:38Z")
ts wrote: > > > > > > “R” == Robert K. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) writes: > > > m[1,1] = 123 > > Try it 🙂 > > moulon% ruby -rmatrix -e ‘m = Matrix[[25, 93], [-1, 66]]; m[1, 1] = > 123’ -e:1: undefined method `[]=’ for Matrix[[25, 93], [-1, > 66]]:Matrix (NoMethodError) moulon% “cool” 🙂 ``` robert ``` ---
**Author:** ![wollez](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/w/58f4c7/32.png) [@wollez](https://www.ruby-forum.com/u/wollez)\ **Post date:** [November 28, 2005, 2:44pm UTC](https://www.ruby-forum.com/t/2dim-array-matrix/48995/8 "2005-11-28T14:44:39Z")
Thanks for the answers, I think I will use for the beginning this solution: mx = Array.new(dim\_x) { Array.new(dim\_y) } for the matrix class: I don’t understand how I can set in a matrix single values: require “matrix” m=Matrix[[25, 93], [-1, 66] ] puts m. this works but when I try: m.=123 puts m I only get an error. Wolfgang