Index exceeds the number of array elements. Index must not exceed 1.

Please help to resolve the error.

clear all; close all; clc;
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%                       Simulation                          %
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%value of constants
a1=0.7;a2=0.1;
omega1=20;omega2=40;
G=10;C12=0;C21=0.003;
dt=0.01;   %step size
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
x1rec(1)=0.5;
y1rec(1)=0.5;
x2rec(1)=0.5;
y2rec(1)=0.5;
for i=2:1000
    x1rec(i)=x1rec(i-1)+((a1-x1rec(i-1)^2-y1rec(i-1)^2)*x1rec(i-1)-omega1*y1rec(i-1)+G*C12*(x2rec(i-1)-x1rec(i-1)))*dt;
    x2rec(i)=x2rec(i-1)+((a2-x2rec(i-1)^2-y2rec(i-1)^2)*x2rec(i-1)-omega2*y2rec(i-1)+G*C21*(x1rec(i-1)-x2rec(i-1)))*dt;
end

Answer 1

[Voss]

The first time through the for loop, i is 2, so on the right-hand side of your equations you are accessing x1rec(1), x2rec(1), y1rec(1), and y2rec(1) and on the left-hand side of your equations you are setting x1rec(2) and x2rec(2).

Then, the second time through the for loop, i is 3, so you are accessing x1rec(2), x2rec(2), y1rec(2), and y2rec(2), but y2rec and y2rec only have one element each. That is, y1rec(2) and y2rec(2) haven't been calculated yet. This is the source of the error.

Maybe your code inside the loop should calculate y1rec(i) and y2rec(i) along with x1rec(i) and x2rec(i) somehow?

[Haya Ali]

Yeah. You are right.

Answer 2

[Jonas]

you can initialize your array before the loop

a1=0.7;a2=0.1;
omega1=20;omega2=40;
G=10;C12=0;C21=0.003;
dt=0.01;   %step size
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
numOfIterations=1000;
x1rec=zeros(1,numOfIterations);
y1rec=zeros(1,numOfIterations);
x2rec=zeros(1,numOfIterations);
y2rec=zeros(1,numOfIterations);

x1rec(1)=0.5;
y1rec(1)=0.5;
x2rec(1)=0.5;
y2rec(1)=0.5;
for i=2:numOfIterations
    x1rec(i)=x1rec(i-1)+((a1-x1rec(i-1)^2-y1rec(i-1)^2)*x1rec(i-1)-omega1*y1rec(i-1)+G*C12*(x2rec(i-1)-x1rec(i-1)))*dt;
    x2rec(i)=x2rec(i-1)+((a2-x2rec(i-1)^2-y2rec(i-1)^2)*x2rec(i-1)-omega2*y2rec(i-1)+G*C21*(x1rec(i-1)-x2rec(i-1)))*dt;
end

disp('finish')

finish

[Haya Ali]

But i should be a graph of oscillations.