Changing the center of rotation to 0 0 doesn't seem to make a difference. 0 1 linrot 1p1;0 0 1.11022e_16 1
But presumably this means I am not understanding what it means to "rotate a linear polynomial"? -- Raul On Thu, Feb 18, 2016 at 11:46 PM, Kip Murray <[email protected]> wrote: > 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 ---------------------------------------------------------------------- For information about J forums see http://www.jsoftware.com/forums.htm
