I am trying to write a code for bisection method using functions but they keep showing me errors in line 24.

function [root,ea,iter]=HomeTask2(f,xi,xf,es,maxit)
  iter=0;
   xm=(xi+xf)/2;
   ab=0;
  while(ab~=1)    
      if (f(xi)*f(xf)>0)
          disp('Error')
          break;
      end  
       if (f(xf)*f(xm)==0) || (f(xi)*f(xm)==0)
         ab=ab+1; 
       end     
        xmold=xm;
        iter=iter+1;
      if (f(xi)*f(xm)<0)
          xf=xm;       
      else
          xi=xm;                       
      end    

    if iter>1
        ea=abs((xm-xmold)/xm)*100; 
    end
                if (ea<=es)||(iter>=maxit)
                    break;
                end
    end
    root=xm;

[Kevin Chng]

which line of code and what is the error?

[Rafin Khan]

Undefined function or variable 'ea'.

Error in HomeTask2 (line 24) if (ea<=es)||(iter>=maxit)

[Rafin Khan]

%also this is the other file I have for calling the function

clc

close all

[root,ea,iter]=HomeTask2(@(x)(x^2)-9,1,7,3,20)

[Kevin Chng]

Hi, take a look at your code

 if iter>1
        ea=abs((xm-xmold)/xm)*100; 
  end

At first line, you assign 0 to iter, therefore your program does not meet the condition enter this if loop as iter must be bigger than 1.

So when come to line

if (ea<=es)||(iter>=maxit)

There is no value been assigned for ea. That's why return error to you.

So far, you did good work, try again. I guess you might need to take a look at your bisection logic again.

[Rafin Khan]

Thanks I will keep trying