Create an Array with Nested Loops

I wish to create a matrix from a set of arrays generated in a loop

So for example: I have a for loop that creates 10 values of y and stores them in a 10 element row vector.

If y is a function of a random variable, and I want to perform 50 evaluations of y over a distribution of it's random variable then I need to vertically concatenate 50 10-element row vectors into a 10X50 element matrix.

So I was trying to use nested loops and can't seem to successfully add all of the vectors into a matrix. The problem is probably notational. I would also be interested in any easier ways to do this.

here is the script: Don't know if i need to create the randomly distributed parameter vector in the beginning or if it can be taken care of in the nested loop.

%Script that samples for yield based on normal distribution and does a MC

% Initialize Random Sampling Values and Loop
MCnumb=500;  % number of monte carlo iterations
MCits=(0:MCnumb); % generate MC loop variable

Y0=0.42 % mg VSSa/mgBODL 
clear Y; % Clear Variable
Y(1)=Y0 % Initial value for yield

for j=1:length(MCits-1),  %Set up for loop for MC 

      Y(j+1)=(Y(j)*rand(1)/Y(j));
  end

      %Script that demonstrates Euler integration for a Monod Model
      % The problem set to be solved is:    % S'=((-q*S(t))/(K+S(t)))*X(t);
    % X'=Y*(((q*S(t))/(K+S(t))-b-(k2h/1.42))*X(t);

    % Define Parameters;
    q=10; % mgBODl/mgVSSa-day
    K=20; % mgBODl/l
    b=0.15; % 1/day
    k2h=0.09; % mgCODP/mgVSSa-day

    %Define Initial Conditions;
    S0=500; % mg/L
    X0=20;   % mg/L

    %Initialize Time Set and Step Size

    h=0.01;    %h is the time step.
    tend=2;     %tend is end of approximation in days
    t=.1:h:tend;  %initialize time variable.

    clear Substrate;  %wipe out old variables.
    clear Biomass;

    Sub(1)=S0;  %initial condition (same for approximation).
    Biomass(1)=X0;

for j=1:length(Y)-1,

    for i=1:length(t)-1,  %Set up "for" loop.
        Srate(i)=-((q*Sub(i))/(K+Sub(i)))*Biomass(i);  %Calculate derivative (rate);
        Xrate(i)=Y(j)*((q*Sub(i))/(K+Sub(i))-b-(k2h/1.42))*Biomass(i);

        Sub(i+1)=Sub(i)+h*Srate(i);  %Estimate new concentrations;
        Biomass(i+1)=Biomass(i)+h*Xrate(i);

        Substrate(j+1)=Sub(i);

    end

SJ(j)=vertcat(Substrate(j),Substrate(j+1))
end

Answer 1

[Sean de Wolski]

Could you boil this down to a small example? It looks like you're missing the ':' necessary to specify all columns or all rows. Not really sure though.

SJ(:,j) %all rows in column j

or similar

Answer 2

[Richard]

Thank you, that was the issue, Here is a sample code for anyone else that looks.

%Nested Loop Builds Array

for j=1:4
    L(j,:)=vertcat(y(i));
for i=1:10
    y(i+1)=rand+y(i)
end
endplot(y)
L