Help with bisection method

I am having trouble with this code for the bisection method. It keeps outputting an answer of 1 no matter how many iterations I put, but that is not the root of this equation. I also don't know how to output a table for each iteration.

function Bisect(xl, xu, es, imax, xr, it, ea)
f =@(x) exp(-x) - x;
it = 0;
fl = f(xl);
 
xrold = xr;
xr = (xl + xu) / 2;
fr = f(xr);
it = it + 1;

if xr ~= 0 
 ea = abs((xr - xrold) / xr) * 100;
end
    if (fl * fr) < 0
    xu = xr;
    else if (fl * fr) > 0 
    xl = xr;
    fl = fr;
    else
    ea = 0;
 end
end
 
if ea < es, or iter >= imax
end
 Bisect = xr
end 

Answer 1

[David Hill]

function bisect= Bisect(f,xl, xu, es, imax)%recommend imputting the function
it=0;
ea=1;
xr = (xl + xu) / 2;
while ea>es && it<imax % you need a loop
 fr = f(xr);fl = f(xl);
 it = it + 1;
 if (fl * fr) < 0
    xu = xr;
 elseif (fl * fr) > 0 
    xl = xr;
 else
    ea = 0;
 end
 xrold=xr;
 xr = (xl + xu) / 2;
 ea = abs((xr - xrold) / xr) * 100;
 bisect(it)=xr;%index to maintain all interations of xr's
end
end 

Then call the function Bisect(). Index whatever you want to provide in a table and assemble the table outside the loop.

bisect=Bisect(@(x)exp(-x)-x,0,1,1e-14,100);
bisect(end)
ans =

   0.567143290409784

[Lauren Holm]

I can't say thank you enough!!!!!! THANK YOU :)))))))!