MATLAB: How to solve ‘Index exceeds the number of array elements (1)’

MATLAB

[MATLAB is showing this error "Index exceeds the number of array elements (1)

Best Answer

Your x and y are single value, so it will have error when i==2.

You can make use of 'Pause on Errors' under the drop down menu of Run to analyse what's going wrong with the variables.

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MATLAB: Solving Lorenz attractor equations using Runge kutta (RK4) method

The only bug that I can see at first glance is here

 y(i+1) = y(i) + h*(1/6)*(l1+2*l2+2*l3+l4); % replace ki by li

You also might want to play with (decrease) the step size.

MATLAB: I don not get the graph when i add A1(x) in the function f1=@(x,y) A1(x)+(1.33pietay^3)/(1+1.33pietay^3);

Do not use the for loop here. Let vectorisation work for you.

Try this:

eta=0.25;
L=2.5;
a=0.1;
h=0.1;
b=6;
x=a:h:b;
%%%%%%%%%%%%%%%%%%
A =@(x) (0<x).*1+(0<=x & x<=L).*(1+0.5*(1-cos(2*pi*x/L)).^1/2) + (L<x).*1;
A1=@(x) (gradient(A(x))./gradient(x));
f1=@(x,y) A1(x)+(1.33*pi*eta*y.^3)./(1+1.33*pi*eta*y.^3);
y(1)=01;
% for i=1:length(x)-1;   
   k1=h*f1(x,y);
   k2=h*f1(x+0.5*h,y+.5*k1);
   k3=h*f1(x+.5*h,y+.5*k2);
   k4=h*f1(x+h,y+k3);
  y = +(1/6)*(k1+2*k2+2*k3+k4);  
% end
plot(x,y)

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MATLAB: Solving Lorenz attractor equations using Runge kutta (RK4) method

MATLAB: I don not get the graph when i add A1(x) in the function f1=@(x,y) A1(x)+(1.3​3*pi*eta*y​^3)/(1+1.3​3*pi*eta*y​^3);

Related Question

MATLAB: I don not get the graph when i add A1(x) in the function f1=@(x,y) A1(x)+(1.33pietay^3)/(1+1.33pietay^3);