I'm glad to be rid of the problem. Thanks. Linda
-----Original Message----- From: programming-boun...@forums.jsoftware.com [mailto:programming-boun...@forums.jsoftware.com] On Behalf Of km Sent: Sunday, February 24, 2013 1:40 AM To: programm...@jsoftware.com Subject: Re: [Jprogramming] The farmer's fence The problem goes away if you use {: instead of }. in your definition of r . r1 =: [: > [: {: p. r1 0 100 _2 50 0 a r1 0 100 _2 25 The problem you had is caused by the fact that }. applied to a vector always has a vector result and is solved by the fact that {: applied to a vector always has a scalar result. Someone else will have to explain why opening , <50 0 has a different result from opening <50 0 , and also explain the relevance of the difference. At least I can make the problem go away! Kip Sent from my iPad On Feb 23, 2013, at 10:34 PM, "Linda Alvord" <lindaalv...@verizon.net> wrote: > My first line select the two roots: > > r=: 13 :'> }. p. y' > r 0 100 _2 > 50 0 > > These are the roots: > > Now find the axis of symmetry x value (the average of the roots, > > a=: 13 :'(+/y)%#y' > a 50 0 > 25 > > So if I apply a to r 0 100 _2 I expect 25. I get 1 2 > > > > > -----OriginalaMessage----- > From: programming-boun...@forums.jsoftware.com > [mailto:programming-boun...@forums.jsoftware.com] On Behalf Of km > Sent: Saturday, February 23, 2013 9:53 PM > To: programm...@jsoftware.com > Subject: Re: [Jprogramming] The farmer's fence > > Linda, if you enter 50 0 and then enter 1 2 $ 50 0 the printed > results appear the same, but the first has two items and the second only one item. > What do you expect the average of a one-item array to be? Can you > figure out how to use rank to get what you want from r 0 100 _2 ? > > Sent from my iPad > > > On Feb 23, 2013, at 6:21 PM, "Linda Alvord" <lindaalv...@verizon.net> wrote: > >> A should give an average. The roots are 50 0 . >> >> Shouldn't the average be 25 rather than 1 2 ? >> >> Linda >> >> -----Original Message----- >> From: programming-boun...@forums.jsoftware.com >> [mailto:programming-boun...@forums.jsoftware.com] On Behalf Of km >> Sent: Saturday, February 23, 2013 6:45 PM >> To: programm...@jsoftware.com >> Subject: Re: [Jprogramming] The farmer's fence >> >> r 0 100 _2 >> 50 0 >> $r 0 100 _2 >> 1 2 >> >> Sent from my iPad >> >> >> On Feb 23, 2013, at 4:35 PM, "Linda Alvord" <lindaalv...@verizon.net> > wrote: >> >>> The roots of a polynomial: >>> >>> r=: 13 :'> }. p. y' >>> r 0 100 _2 : >>> 50 0 >>> r >>> [: > [: }. p. >>> >>> >>> The average of the roots or x coordinate of axis of symmetry: >>> a=: 13 :'(+/y)%#y' >>> a 50 0 >>> 25 >>> a >>> +/ % # >>> >>> Find the maximum: >>> >>> 0 100 _2 p. 25 >>> 1250m >>> >>> Sadly this doesn't work: >>> >>> a r 0 100 _2 >>> 50 0 >>> >>> Any idea why not? >>> >>> Linda >>> >>> >>> -----Original Message----- >>> From: programming-boun...@forums.jsoftware.com >>> [mailto:programming-boun...@forums.jsoftware.com] On Behalf Of Alex >>> Giannakopoulos >>> Sent: Saturday, February 23, 2013 3:28 PM >>> To: J Programming forum >>> Subject: Re: [Jprogramming] The farmer's fence >>> >>> Nice little gotcha there, assuming that the shape will be a square, >>> since a square maximizes the contained area for a rectangle, while >>> forgetting that the wall gives you extra perimeter for free, >>> depending on >> the shape. >>> >>> By the same analogy I'd tackle Roger's version of the problem, i.e. >>> find ANY shape that will maximize the area: >>> Again, I suspect that going for a (semi)circle might be essentially >>> the same gotcha. >>> >>> I haven't got time to code it at the moment, but I'd investigate an >>> (half) ellipse and also a parabola. >>> Will need some integration though, to find the expression for the >>> length of their curves. >>> -------------------------------------------------------------------- >>> - >>> - For information about J forums see >>> 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 >> >> --------------------------------------------------------------------- >> - For information about J forums see >> 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 ---------------------------------------------------------------------- For information about J forums see http://www.jsoftware.com/forums.htm ---------------------------------------------------------------------- For information about J forums see http://www.jsoftware.com/forums.htm
