CODEWITHSUNDEEP
matlab
Badr
Badr

Reputation: 1

Use the bisection method to find solutions in Matlab?

I am trying to solve the following question:

Use the bisection method to find solutions accurate to within 10^−4 on the interval [−5, 5] of the following functions:

f(x)= x^5-10x^3-4

This is my code:

function sol=bisect(fn,a,b,tol)

%Bisection method for the Nonlinear Function
fa=feval(fn,a);fb=feval(fn,b);
if fa*fb>0;fprintf('Endpoints have same sign')
   return
end
k=0;
while abs (b - a)>tol
   c =(a+b)/2;
   fc=feval(fn,c);
   if fa*fc < 0; b=c; else a = c; 
       k=k+1;
   end
end
sol=(a+b)/2;

When I run the program, I do:

a= -5
b=5
fn =  x^5-10x^3-4

But the last line returns an error:

undefined function or variable x

Upvotes: 0

Views: 838

Answers (1)

Ander Biguri
Ander Biguri

Reputation: 35525

to define an equation that can be evaluated by feval, you need to define as a function.

Try defining fn as fn=@(x)(x^5-10x^3-4). This way you can use feval(fn,3).

Upvotes: 1

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