why is my for loop not working?

y=@(x) x^2-4;
x1=input('Enter the value of x1:');
x2=input('Enter the value of x2:');
x3=input('Enter the value of x3:');
for i=1:100
    L1=(x2-x3)/(x3-x1);
    xf=x3+L1*(x3-x1);
    y1=abs(y(x1));
    y2= abs(y(x2));
    y3=abs(y(x3));
    yf=abs(y(xf));
    
    ynext=sort([y1 y2 y3 yf]);
    
    if y1==max(ynext)
        x1=xf;
    elseif y2==max(ynext)
        x2=xf;
    else
        x3=xf;
    end
    if y(xf)<10^-10
        break
    end
    
end
fprintf('the root: %f\n the number of iterations: %d\n',xf,i)

[KIPROTICH KOSGEY]

Anyone out there to shed some light on the above?

[Torsten]

Should your code be an implementation of the secant method to get a root of y ? Or what is its purpose ?

Answer 1

[dpb]

Probably because you're testing floating point values for exact equality -- see isapprox and ismembertol

See the <example in eq for more> for what is likely the cause.