continuous plot of minimization results

Hello,

I'd like to run the fminsearch solver for a couple of times and plot the progress of the minimization (the residual terms) incessantly:

options=optimset('PlotFcns',@plot_optim_out,'MaxIter',100);

for i=1:5
    [x_iter,~,~,output]=fminsearch(fun,x_iter,options);
    ii=ii+output.iterations;
end
 
function [stop] =  plot_optim_out(~,optimValues,~)
global P_diff; global P_hom; global P_c1;
i=optimValues.iteration+evalin('base','ii');
stop = false;
hold on;
plot(i,P_diff/P_c1,'b*',i,P_hom/P_c1,'go');
set(gca,'yscale','log');
drawnow;
end

The plot continues to count, but the axis refreshes, so the plot "forgets" the previous data points. Does anybody have an idea why?

Regards