Extracting data from a plot within a for loop

In MATLAB, I have coded the stochastic simulation algorithm (Gillespie) for a simple birth-death process, and have gotten a plot by using `hold on` in a `for` loop.

I have 100 values of `PStoch` for each `Qp` value, because I have ran 100 simulations for each `Qp` value. The values are hard to see in the plot below because they are all clustered together.

*How can I save the data from the plot in a matrix, so I can do some calculations on them afterward? Specifically, I need a matrix of size 100 x 100 with all `PStoch` values corresponding to each `Qp` value.*

My code is below:

    rng('shuffle')

    %%Pre-defined variables
    Qpvec = logspace(-2,1,100);
    len = length(Qpvec);
    delta = 1e-3;
    P0vec = Qpvec./delta;
    V = [1,-1];
    tmax = 10000;

    %%Begin simulation
    figure(1)
    for k = 1:len
        t0 = 0;
        tspan = t0;
        Qp = Qpvec(k);
        P0 = P0vec(k);
        Pstoch = P0;
        while t0 < tmax && length(Pstoch) < 100
            a = [Qp, delta*P0];
            tau = -log(rand)/sum(a);
            t0 = t0 + tau;
            asum = cumsum(a)/sum(a);
            chosen_reaction = find(rand < asum,1);
            if chosen_reaction == 1;
                P0 = P0 + V(:,1);
            else
                P0 = P0 + V(:,2);
            end
            tspan = [tspan,t0];
            Pstoch = [Pstoch;P0];
        end
        plot(Qp,Pstoch)
        hold on
        axis([0 max(Qp) 0 max(Pstoch)])
    end

The plot is here: http://i.stack.imgur.com/OVTD9.jpg

Thanks for help.

[yamen alharbi]

Hi, hopefully you would probabely have found an answer. I ran into a proble with the stochastic simulation.

I would like to plot different trajectories. could you please shed a light on how to plot multiple paths.

Thaks