[Jprogramming] A plane rotation

[Kip Murray]

Not bad.  I didn't know about r.  .  For clean I use

 clean =: (* *!.1e_14@|)"0&.+.

--Kip

On Tuesday, February 16, 2016, Raul Miller <rauldmiller at gmail.com> wrote:

> Well...
>
>    rottheta=: (rot~ r.)~
>    1r2p1 rottheta 3 4
> _4 3
>    1r4p1 rottheta _1 1
> _1.41421 1.11022e_16
>
> I remember there being a concise phrase to clean irrelevant bits near
> zero in a complex number, but I can't remember what I need to search
> on to find it, and my foggy memory of how to write it is failing me at
> the moment.
>
> Still, this gets you close.
>
> --
> Raul
>
>
> On Tue, Feb 16, 2016 at 11:50 PM, Kip Murray <thekipmurray at gmail.com
> <javascript:;>> wrote:
> > I'm retired with time to "fool around".  Finding an old rot90 verb that
> > used multiplication by a 2 by 2 matrix, I sought a more direct way using
> > complex numbers and found one of the solutions that was posted.  I also
> > learned a lot from the other solutions posted, thanks everyone!
> >
> > New puzzle: find a complex analysis way to do a rotation given its angle
> in
> > radians, examples:
> >
> >     1r2p1 rottheta 3 4
> >  _4 3
> >
> >     1r4p1 rottheta _1 1
> >  _1.414213562 0
> >
> > --Kip
> >
> > I'm also a former math professor!
> >
> > On Tuesday, February 16, 2016, David Lambert <b49p23tivg at gmail.com
> <javascript:;>> wrote:
> >
> >>
> >> what's your agenda, are you writing a book? Isn't there a homogeneous
> >> coordinate system/transformation lab?
> >>
> >>>
> >>> On 02/16/2016 06:16 PM, programming-request at forums.jsoftware.com
> <javascript:;> wrote:
> >>>
> >>>> Date: Tue, 16 Feb 2016 15:18:43 -0600
> >>>> From: Kip Murray<thekipmurray at gmail.com <javascript:;>>
> >>>> To:"programming at jsoftware.com <javascript:;>" <
> programming at jsoftware.com <javascript:;>>
> >>>> Subject: [Jprogramming] A plane rotation
> >>>> Message-ID:
> >>>>     <
> CAOfWorgVyDB1NmJwXkB0WOSYFnLUBXCDZ20sV11ukSFCfay5sA at mail.gmail.com
> <javascript:;>>
> >>>> Content-Type: text/plain; charset=UTF-8
> >>>>
> >>>> Fairly easy: write a verb that rotates a point in the plane by the
> angle
> >>>> of
> >>>> a given complex number.  For example
> >>>>
> >>>>      1j1 rot 1 1  NB. Rotate 1 1 counterclockwise 45 degrees
> >>>>   0 1.414213562
> >>>>
> >>>> Background information:  when you multiply two complex numbers the
> >>>> magnitudes are multiplied and the angles are added.
> >>>>
> >>>> --Kip Murray
> >>>>
> >>>>
> >>>
> >> ----------------------------------------------------------------------
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> >
> >
> >
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