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From: Robert Maxim on 18 Apr 2010 21:56
Is there a quick way in matlab to give me the smallest possible real root of something I am casting a ray with. Newtons, seecannt are too slow.
From: John D'Errico on 18 Apr 2010 22:08
"Robert Maxim" <toejama1(a)gmail.com> wrote in message <hqgd7l$t74$1(a)fred.mathworks.com>...
> Is there a quick way in matlab to give me the smallest possible real root of something I am casting a ray with. Newtons, seecannt are too slow.

Sorry, but um, no.

John
From: Roger Stafford on 18 Apr 2010 22:08
"Robert Maxim" <toejama1(a)gmail.com> wrote in message <hqgd7l$t74$1(a)fred.mathworks.com>...
> Is there a quick way in matlab to give me the smallest possible real root of something I am casting a ray with. Newtons, seecannt are too slow.
----------------
Could you please go into greater detail regarding that phrase "something I am casting a ray with"?

Roger Stafford
From: Robert Maxim on 18 Apr 2010 22:16
I want to cast a ray and find the smallest root where it intersects a surface.
you can easily do this with Newtonns method or Seecant but takes forever to converge and you need a good intervals.

"Roger Stafford" <ellieandrogerxyzzy(a)mindspring.com.invalid> wrote in message <hqgdu5$c5c$1(a)fred.mathworks.com>...
> "Robert Maxim" <toejama1(a)gmail.com> wrote in message <hqgd7l$t74$1(a)fred.mathworks.com>...
> > Is there a quick way in matlab to give me the smallest possible real root of something I am casting a ray with. Newtons, seecannt are too slow.
> ----------------
> Could you please go into greater detail regarding that phrase "something I am casting a ray with"?
>
> Roger Stafford
From: Roger Stafford on 18 Apr 2010 22:36
"Robert Maxim" <toejama1(a)gmail.com> wrote in message <hqged6$jt8$1(a)fred.mathworks.com>...
> I want to cast a ray and find the smallest root where it intersects a surface.
> you can easily do this with Newtonns method or Seecant but takes forever to converge and you need a good intervals.
---------------
By slow tortuous degrees we are managing to extract more information from you about your question, but much more needs to be made clear. Where you say, "cast a ray and find the smallest root where it intersects a surface", is this ray being "cast" from a fixed point above a three-dimensional surface? What is known about the direction of "casting". What is the mathematical form of the surface? What quantity is it you are wishing to find the root of? - the distance to the intersection, the point of intersection? If we don't find out such things as this you may have to be content with John's succinct answer.

Roger Stafford
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