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Topic: help : how to reverse 2-D lookup table ?
Replies: 10   Last Post: Oct 30, 2013 5:54 AM

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John D'Errico

Posts: 9,038
Registered: 12/7/04
Re: help : how to reverse 2-D lookup table ?
Posted: Jan 29, 2010 7:03 AM
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"meng yan" <anoucxy@163.com> wrote in message <hju7lf$e34$1@fred.mathworks.com>...
>
>
> I am trying to reverse a 2D lookup table, i.e.I have T=T(a,b), I need to figure out
> a=a(T,b). Anybody ever tried this before? Any ideas?
> i.e.a=[1 2 3];b=[3 4 5];T=[1 3 4;4 6 5;2 7 6];
> how could I get a as a=[3X3],b=[1X3],T=[1X3]?
> Thanks!


Has anyone ever "tried it before"?

Why do I need to have tried something that is not
possible in general, or if possible, is trivial to do?

Depending upon the shape of the function T(a,b),
there may be multiple solutions, so this will not
be possible. Even if it is possible because of a
strictly monotonic response, then there may be
only a limited set of solutions for certain values of
T. But for those values of T such the a solution
exists, it will be trivial to compute. Simply fix
the value of b, and interpolate. WTP?

John



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