Problem with cumtrapz

Hi,
I want to integrate the discrete function rho*x_n*(1-x_n) from nr to t (take r=0.005)
> > where rho:0:0.001:4 and n=0,1,2,3,...., and t\in[nr,(n+1) r]
% define the vector of colors, to plot the data of reach value of r in
% different color
color_vec = ['b'];
r=0.05;
for rho = 0: 0.001:10
% define the number of discrete times in interval [k*r, (k+1)*r]
n = 50;
% define the number of iterations k = 1,.....,Nit
Nit = 150;
% define the initial vector which is a vector of size n
x0 = 0.3*ones(1,n);
% define vectors x_next and x_previous
x_next = zeros(1,n); %x_(n+1)
x_previous = zeros(1,n); %x_n
time = zeros(1,n);
% initialize x_previous
x_previous = x0;
x_next = x_previous;
hold on
for i = 1:Nit
time = linspace(i*r,(i+1)*r,Nit);
y_next=rho.*x_previous.*(1-x_previous);
x_next = x_previous+ cumtrapz(y_next);
x_previous = x_next;
end
end
plot(rho,x_next(1),'.', 'Color', char(color_vec))
Now I have only one point in the plot!! I also want to integrate from n*r to t!?
Any help please.
thanks a lot in advance