
Re: help : how to reverse 2D lookup table ?
Posted:
Jan 29, 2010 7:56 PM


"John D'Errico" <woodchips@rochester.rr.com> wrote in message <hjuipn$bmr$1@fred.mathworks.com>... > "meng yan" <anoucxy@163.com> wrote in message <hju7lf$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 May be should use others means, the datas of T=T(a,b) are got by inner compute of matlab using Finit Element Analysis ,so I think it cann't simplly get a(a=a(T,b)), but there must have a means to do that . I aways try to use matlab's data process to achieve it ,but all have failed. Who have a good idears ? meng yan

