plot objective function result versus number of generations

i have two m files one of them is the main and the other is the objective function . the file of the objective function have the variables that i want to plot versus the number of generations ,how to plot KP versus number of generations ? this is objective file

    % %PID_objfun_ITAE.m
%____________________________________________________________________
function [ fx_val]=PID_objfun_ITAE(x_pop,options)

KP=x_pop(1); KI=x_pop(2)

%____________________________________________________________________ simopt = simset('solver','ode45','SrcWorkspace','Current','DstWorkspace','Current'); % Initialize sim options [tout,xout,yout,u] = sim('pid_INC_GA',[],simopt); yout; t =0:0.1:41; %[y t] = step(sys_controlled,time); % Step response of closed-loop

for i=1:401 error(i) = (abs(-26.3+yout(i)))*t(i);

end

ITAE=sum(error); %__________________________________________________________________

 fx_val= ITAE

[mado]

any help??