Resolution of equation under constraints with 'fminbnd'

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studentU 2015-6-23

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评论： Walter Roberson 2015-6-26

hi, i must resolve the system of equations with two variable x and y, and i use 'solve' to do it, but i must limit the solution between an interval, can fminbnd function replace 'solve' in this case

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studentU 2015-6-23

编辑：studentU 2015-6-23

thank's for ue repply, YES, i have tow equations with tow unknows, and my system can have multiple solutions.

Torsten 2015-6-23

在 MATLAB Online 中打开

The reason why I ask is that it is usually not possible to restrict the solution to a certain interval.

The best you can expect is to get values for x and y such that

f1(x,y)^2+f2(x,y)^2

is minimized if you want to solve

f1(x,y)=0 and f2(x,y)=0.

If this is what you want you can proceed as Matt suggested.

Best wishes

Torsten.

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回答（1 个）

Matt J 2015-6-23

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No, fminbnd only handles problems in a single unknown. You can use lsqnonlin, if you have the Optimization Toolbox, or you can try things on the File Exchange, like fminsearchbnd

http://www.mathworks.com/matlabcentral/fileexchange/8277-fminsearchbnd--fminsearchcon

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studentU 2015-6-26

it become already error: Failure in initial user-supplied objective function evaluation. LSQNONLIN cannot continue.

Walter Roberson 2015-6-26

Your x0, your initial points, is -pi/2 which is a scalar. But your objective function expects a vector of length two (or more). You need to supply a vector of length 2 instead of -pi/2

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