Re: matlab rotx, roty, rotz, function and equivalent in octave 4.0 or packages

[JuanPi]

On Mon, Apr 10, 2017 at 12:51 PM, Nicholas Jankowski
<address@hidden> wrote:
> On Apr 9, 2017 8:32 PM, "Nicholas Jankowski" <address@hidden> wrote:
>
> On Fri, Apr 7, 2017 at 9:42 AM, Olaf Till <address@hidden> wrote:
>>
>> On Fri, Apr 07, 2017 at 07:17:24AM -0400, RT wrote:
>> > Greetings,  does Octave 4.0 or one of it's packages have an equivalent
>> > to
>> > Matlabs rotx, roty, rotz, function
>> > https://www.mathworks.com/help/phased/ref/rotx.html
>>
>> The geometry package has similar functions. CCing the maintainer.
>>
>>
>
> with a quick peek geometry seems to have some similar functionality but not
> matlab compatible versions of those functions.
>
> createRotation would recreate rotz if it took degrees by default.
>
> the 3d rotation functions createRotationOx, createRotationOy, and
> createRotationOz would work if they weren't 4x4 matrices.  (why are they
> 4x4? what's the 4th value, length which stays invariant?
>
> aliases could easily be created for those to implement the rot functions.
> That said, the actual implementation is so simple it's almost a shame to add
> the overhead of the extra function call to create them.
>
> in Matlab, rotx, roty, and rotz appear to be part of the Phased Array System
> Toolbox.
>
>>> which rotx
> C:\Program Files\MATLAB\R2016b\toolbox\phased\phased\rotx.m
>
>
>
>
> FYI to close the loop on this I did submit a set of functions to the bug
> tracker for this.
>
> http://savannah.gnu.org/bugs/?50772

Hi,

if your functions get into core, I will definitely make the geometry
functions just wrappers to them.
The functions return 3x3 (2d) and 4x4(3d) matrices because they
implement affine transformations using homogeneous coordinates[1]. In
this way, e.g., it is easy to define a rotation around an arbitrary
point in space.

[1]: https://en.wikipedia.org/wiki/Homogeneous_coordinates

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