solve a set of two linear equations

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mary 2021-10-1

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编辑： Alan Weiss 2021-10-3

Hello,

I have a set of two linear equations. I know how to solve it on paper. The only issue is how to make a well-structured code for it by using function handels (so without using symolic variables). Let's consider the following example:

f1 = @(x,y) y - x - a(x) - b(y) + cst1 ;
f2 = @(x,y) y - x - c(x) - d(y) + cst2 ;

a and c are functions of x, b and d functions of y, cst 1 and cst 2 are constants.

Thanks in advance for your help.

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Answer 1

Steven Lord 2021-10-1

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If this isn't a homework assignment, use fsolve from Optimization Toolbox.

If this is a homework assignment, check your textbook to see if there is an algorithm and/or pseudocode that you can implement as MATLAB code. If there is but you aren't sure where to start because you're not familiar with how to write MATLAB code, I suggest you start with the free MATLAB Onramp tutorial (https://www.mathworks.com/support/learn-with-matlab-tutorials.html) to quickly learn the essentials of MATLAB.

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mary 2021-10-1

No, it is not a homework and I am familiar with Matlab. The only problem is that I dont see how to use fsolve with function handels (f1 = @(x,y) ... and f2 = @(x,y) ...). Here: https://nl.mathworks.com/help/optim/ug/fsolve.html, for instance F1 and F2 are not function handles. I want to use function handle for the sake of clarity of the code (as each equation includes many terms depending on x and y like a(x) or b(y) in the above example). I dont want to use symbolic parameters neither. Is there any way to use fsolve with my f1(x,y) and f2(x,y) ?

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Answer 2

Alan Weiss 2021-10-3

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编辑：Alan Weiss 2021-10-3

I don't really understand what you are trying to do, but it sounds to me like your best bet is to use the Problem-Based Optimization Workflow or more specifically the Problem-Based Workflow for Solving Equations. You can write your optimization variables with perfect clarity, and your will get the same underlying solver (fsolve) if it is appropriate.

Alan Weiss

MATLAB mathematical toolbox documentation