No, because his center of rotation is not 0 0 . In his first two examples the center of rotation is 0 1 and in the third it is 1 1 . --Kip
On Thursday, February 18, 2016, Raul Miller <[email protected]> wrote: > I'm not quite sure I follow what you are doing here. > > Shouldn't 2p1 be a neutral rotation, with 1p1 being a reversal of > direction? > > Thanks, > > -- > Raul > > > On Thu, Feb 18, 2016 at 10:23 PM, Louis de Forcrand <[email protected] > <javascript:;>> wrote: > > To continue with the rotation challenges, write a verb that rotates a > linear > > polynomial (coeffs in x) by 0 {:: y with a centre of 1 {:: y: > > > > 1 2 linrot 1p1 ; 0 1 > > 1 2 > > 1 2 linrot 1r2p1 ; 0 1 > > 1 _0.5 > > 1 2 linrot 1p1;1 1 > > _3 2 > > > > My take: > > linrot=: ({: %. 1 ,. {.)@rotposmat > > rotposmat=: centre + j./@posmat |:@:+.@:* r.@angle > > centre=: 1&({::)@] > > posmat=: (] ,: p.)&0 1@[ - centre > > angle=: 0&({::)@] > > > > It uses matrix division on a rotated set of two points from the original > > polynomial. Not very elegant, but I’m pretty sure it works. > > > > Best regards, > > Louis > > > >> On 17 Feb 2016, at 06:40, Kip Murray <[email protected] > <javascript:;>> wrote: > >> > >> Not bad. I didn't know about r. . For clean I use > >> > >> clean =: (* *!.1e_14@|)"0&.+. > >> > >> --Kip > >> > >> On Tuesday, February 16, 2016, Raul Miller <[email protected] > <javascript:;> <mailto:[email protected] <javascript:;>>> 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 <[email protected] > <javascript:;> > >>> <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 <[email protected] > <javascript:;> > >>> <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, [email protected] > <javascript:;> > >>> <javascript:;> wrote: > >>>>>> > >>>>>>> Date: Tue, 16 Feb 2016 15:18:43 -0600 > >>>>>>> From: Kip Murray<[email protected] <javascript:;> > <javascript:;>> > >>>>>>> To:"[email protected] <javascript:;> <javascript:;>" < > >>> [email protected] <javascript:;> <javascript:;>> > >>>>>>> Subject: [Jprogramming] A plane rotation > >>>>>>> Message-ID: > >>>>>>> < > >>> caofworgvydb1nmjwxkb0wosyfnlubxcdz20sv11uksfcfay...@mail.gmail.com > <javascript:;> > >>> <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 > >>>>>>> > >>>>>>> > >>>>>> > >>>>> > ---------------------------------------------------------------------- > >>>>> For information about J forums see > http://www.jsoftware.com/forums.htm > >>>> > >>>> > >>>> > >>>> -- > >>>> Sent from Gmail Mobile > >>>> ---------------------------------------------------------------------- > >>>> For information about J forums see > http://www.jsoftware.com/forums.htm > >>> ---------------------------------------------------------------------- > >>> For information about J forums see http://www.jsoftware.com/forums.htm > >> > >> > >> > >> -- > >> Sent from Gmail Mobile > >> ---------------------------------------------------------------------- > >> For information about J forums see http://www.jsoftware.com/forums.htm > <http://www.jsoftware.com/forums.htm> > > ---------------------------------------------------------------------- > > For information about J forums see http://www.jsoftware.com/forums.htm > ---------------------------------------------------------------------- > For information about J forums see http://www.jsoftware.com/forums.htm -- Sent from Gmail Mobile ---------------------------------------------------------------------- For information about J forums see http://www.jsoftware.com/forums.htm
