*To*: debian-laptop@lists.debian.org, Paul Anzel <panzel@caltech.edu>*Subject*: Re: Matrix rotation*From*: Norbert X <nrbrtx@gmail.com>*Date*: Sat, 09 May 2015 09:14:22 +0400*Message-id*: <[🔎] 6pbkmcum5woo15yy806vx4i5.1431148096382@email.android.com>*In-reply-to*: <0ak5onclt5rr9dqn884iah82.1431147885560@email.android.com>*References*: <0ak5onclt5rr9dqn884iah82.1431147885560@email.android.com>

Dear Arghya Das!

I think you can start learning matrixes with more high-level language - for example Scilab or Octave.

Then you can switch to low-level languages - C/C++ (with Boost library) or Fortran.

With best regards,

Norbert.

P.S. Of course this problem is out of topic. I recommend you to search or ask on

https://math.stackexchange.com too.

----Пользователь Paul Anzel написал ----

Are you trying to cyclically permute the columns of a matrix? So for a

3x3 matrix of columns [A, B, C] you want [C, A, B]? Then you'd right

multiply (X_new = X*M) by a matrix M =

[0, 1, 0]

[0, 0, 1]

[1, 0, 0]

(generalizing to higher dimensions is trivial).

And yes, this is not a particularly debian-laptop appropriate question.

For math questions of this sort, I'd recommend browsing/posting at

https://math.stackexchange.com/

On 05/08/2015 02:24 PM, giulianc51 wrote:

> Il giorno Sat, 9 May 2015 01:21:44 +0530

> Arghya Das <arghya0190@gmail.com> ha scritto:

>

> Hi Arghya,

> (sorry for my bad english)

>

>

>> Does anyone know how to rotate a 2d matrix circularly for 'n' times in

>> suppose C language...? It would be a lot of help if you could explain

>> with code.

> I don't understand your _expression_ "rotate a 2d matrix circularly"; as

> Jan-Rens explained you, you can build a matrix

> M = | cos(theta) sin(theta)|

> |-sin(theta) cos(theta)|

> and a vector

> X = | x |

> | y |

> (in linear algebra the vectors are column-wise); if you repeat the

> multiplication X = M*X you have a series of vectors X, each rotating a

> theta angle respect to the previous one;

>

> best regards,

> giuliano

>

>

> PS: if you want you can operate with row vectors using the

> transposition X = X*transpose(M), but normally, as I said, the vectors

> are disposed as column;

>

>

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