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

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Haya Ali on 6 Feb 2023
Commented: Haya Ali on 7 Feb 2023
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
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### Accepted Answer

Voss on 6 Feb 2023
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?
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Haya Ali on 7 Feb 2023
Yeah. You are right.

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### More Answers (1)

Jonas on 6 Feb 2023
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
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Haya Ali on 6 Feb 2023
But i should be a graph of oscillations.

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