Saving for loop output ever iteration

I would like to save the output from the second for loop every iteration so that I can plot it vs the variable G at the end. I can't figure out the problem. The code:

% Chaos Theory - Mapping Chaotic Behavior

clc
clear all

n = 0; 

size = 100; % Size of chaotic array

x = 0.5; % Initial value

xnew = zeros(101,size-1); %Initializes Array

for j = 1:101
    
   
    G = 2.9 + n;
    
    for i = 1:size-1
         
        x(i+1) = G*x(i)*(1-x(i)); % Mapping Equation
        
    end
    
    xnew(i) = x;
    
    n = n + 0.01;
    
% Use if animated plot is desired. Slows down simulation time.
%     figure(1)
%     hold on
%     plot(G,x,'r.')

end

   
    figure(1)
    hold on
    plot(G,xnew,'r.')

Answer 1

[Cris LaPierre]

There are some issues:

1. you are not capturing/saving every value of G. You probably want to use loop counter j. G(j) = 2.9+n;
2. You are saving x using loop counter i. I think you want to use loop counter j.
3. When plotting, MATLAB treats columns as series, not rows. If you want to plot G vs x, you need your series data to be in columns (assign x to a column in xnew, not a row). Same goes for G - series value goes in corresponding column. Also means swapping your preallocation dimensions - zeros(size-1,101).
4. The output of the second for loop is a vector. You are getting an error on the assignment because of that. Your preallocation of xnew suggests you need to specify what rows and column to assign x to: xnew(:,j) = x;
5. There is a mismatch between what the size of x is, and what the size of xnew is. You likely don't want to include the initial value for x, so when allocating to xnew, use xnew(:,j) = x(2:end)

Try this:

% Chaos Theory - Mapping Chaotic Behavior
n = 0; 
size = 100; % Size of chaotic array
x = 0.5; % Initial value
xnew = zeros(size-1,101); %Initializes Array
for j = 1:101
    G(j) = 2.9+n;
    for i = 1:size-1
        x(i+1) = G(j)*x(i)*(1-x(i)); % Mapping Equation
    end
    xnew(:,j) = x(2:end);
    n = n + 0.01;
end
plot(G,xnew,'r.')

I get this figure:

[Kelly McGuire]

Excellent! I was missing G and xnew. Thanks!