MATLAB: How to save the error data for each iteration

mathematicsMATLABmatlab functionplot

Hello,
I have a bisection function code that doesn't quite do what I want it to do. I want it to output the error data for each iteration. Right now, it's only giving me the final error value. I know I'm supposed to do err = [] or something like that but I haven't been able to implement it correctly. Could I please get some assistance? Thank you
function [x_i,err,yi] = bisect(f,x_l,x_r,delta)
yl = feval(f,x_l);
yr = feval(f,x_r);
err = [];
if yl*yr > 0
 disp('error'),0;
else
max1 = 1+round((log(x_r-x_l)-log(delta))/log(2));
  for k = 1:max1
	x_i = (x_l+x_r)/2;
	yi = feval(f,x_i);
	if yi == 0
		x_l = x_i;
		x_r = x_i;
	elseif yr*yi > 0
		x_r = x_i;
		yr = yi;
	else
		x_l = x_i;
		yl = yi;
	end
	if x_r-x_l < delta, break,end
  end
end
x_i = (x_l+x_r)/2;
err = abs(x_r-x_l);
yi = feval(f,x_i);

Best Answer

hello
simply put err computation in the main loop and index it 
function [x_i,err,yi] = bisect(f,x_l,x_r,delta)
yl = feval(f,x_l);
yr = feval(f,x_r);
err = [];
    if yl*yr > 0
     disp('error'),0;
    else
    max1 = 1+round((log(x_r-x_l)-log(delta))/log(2));
          for k = 1:max1
            x_i = (x_l+x_r)/2;
            yi = feval(f,x_i);
            if yi == 0
                x_l = x_i;
                x_r = x_i;
            elseif yr*yi > 0
                x_r = x_i;
                yr = yi;
            else
                x_l = x_i;
                yl = yi;
            end
            err(k) = abs(x_r-x_l); %% here
%             if x_r-x_l < delta, break,end
            if err(k) < delta, break,end   %% and here
            
          end
    end
x_i = (x_l+x_r)/2;
% err = abs(x_r-x_l); % remove here
yi = feval(f,x_i);
end
Related Question