How to solve the error and get p2 value?

when i Run this code got

Error: Index exceeds matrix dimensions.

please anyone tell me my mistakes....and How to get p2 value....

Thanks...

Answer 1

[Mathieu NOE]

hello

your errors are due to trying to access a structure in a wrong way , like :

m1=xa(end,2);

I suppose the intention is to access the y output in this structure

so it should be :

m1=xa.y(end,2);

but this is the second sample of the simulation, and I guess what you wanted is to have the last sample , 2nd row of the y array

xa = struct with fields:

solver: 'ode45'

extdata: [1×1 struct]

x: [1×889 double]

y: [6×889 double]

stats: [1×1 struct]

idata: [1×1 struct]

so I suppose this is the correct output :

m1=xa.y(2,end);

but I am surprised to see very big numbers , and also the plot is a bit strange with only a straight line , so I wonder where we still have trouble with your code.

I also added "hold on" after your plot command as I guess you want to have all points of your loop being plotted

clc;
clear all;
t=linspace(0,1,10);
M=0.5;
beta=0.5;
p1=0.1;
p2=0.5;
f=@(t,x) [x(2);x(3);2*x(2).^2+2*(x(2)*x(5))-x(1)*x(3)-x(3)*x(4)+M.^2*x(2)/(1+1./beta);
            x(5);x(6);2*x(5).^2+2*(x(2)*x(5))-x(1)*x(6)-x(4)*x(6)+M.^2*x(5)/(1+1./beta)];
 err_threshold=1e-3;
 iterator =1;
 err=1; 
 while err > err_threshold
    if iterator == 1 
        xa=ode45(f,[0 10],[0 1 p1 0 0.3 0]);
       % ylim([0 5]);
     %plot(t,x(:,3),'--')
%      m1=xa(end,2);  % your code 
%      m1=xa.y(end,2);  % correction # 1 
     m1=xa.y(2,end);    % my guess ?     
     %.........................................
     xa=ode45(f,[0 10],[0 1 p2 0 0.3 0]);
%      m2=xa(end,3); 
%      m2=xa.y(end,3);  % correction # 1
     m2=xa.y(3,end);    % my guess      
     
     plot([p1 p2],[m1 m2]);hold on
    else
        p2=(p2-p1)/(m2-m1)*(1.0-m1)+p1;
        xa=ode45(f,[0 10],[0 1 p2 0 0.3 0]);
%      m2=xa(end,2);  % your code
%      m2=xa.y(end,2); % correction # 1
     m2=xa.y(2,end);    % my guess 
     
     plot([p2,m2]);
     err=abs(1-m2);
    end    
     iterator=iterator+1;
    end

[Priya M]

Thank you so much sir..

[Mathieu NOE]

My pleasure !