CODEWITHSUNDEEP
matlab
Isma Haro
Isma Haro

Reputation: 263

function or method 'ge' for input arguments of type 'sym'

Help! I dont understand whats happening here.

My code:

function y = bisection(TOL, a, b, f) 
pm = (a+b)/2;
fprintf('\t--- METODO de Biseccion ---\n\tFuncion: "%s"\n', char(f));
fprintf('\tIntervalo: [%f,%f]\n',a,b);
fprintf('\t----a----\t----b----\t----pm---\t---f(a)---\t---f(b)---\t---f(pm)---\n');
while (abs(a-b) >= TOL) && (abs(subs(f,pm)+0)>= TOL)
    pm = (a+b)/2;
    fa  = subs(f,a);
    fb  = subs(f,b);
    fpm = subs(f,pm);
    fprintf('\t%f,\t%f,\t%f,\t%f,\t%f,\t%f\n',a,b,pm,fa,fb,fpm);
    if (fa*fb >= 0 )
        error('ERROR, no hay raiz');
    end
    if ( fpm * fa < 0)
        b = pm;
    else
        if ( fpm * fb <0 )
            a = pm;
        end
    end
end
%disp(pm);
fprintf('\tRaiz: %f\n',pm);
y = pm;
return;
end

And I'm calling the function with this

g = x^2-4*x+4 -(log(x));
p = bisection(10^-2,1,2,g);

I think it has to do with logarithm

Upvotes: 0

Views: 207

Answers (1)

crowdedComputeeer
crowdedComputeeer

Reputation: 469

I'm going to guess- always include the error message verbatim and the context code for better help.

I think you've created g as a sym type. You can't use >= or ge with syms because, being symbolic, their are no numbers to compare to.

You could use assume to set bounds on f, but I don't think that will work for your application.

Instead of making x symbolic, make g an anonymous function. 

g = @(x) x^2-4*x+4 -(log(x));
p = bisection(10^-2,1,2,g);

Then, in your function you'll need to replace all occurrences of 

subs(f, a);

With

f(a)

Which will evaluate the anonymous function for the value a. 

>> g(2.3)

ans = 

              -0.7429

Upvotes: 1

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