trying to use heun's method to solve an ode

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Anas Gharsa 2022-1-27

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1637425-trying-to-use-heun-s-method-to-solve-an-ode

编辑： Torsten 2022-1-28

I am trying for days to solve an ode using heun's method for a project but i always keep getting an error message!!!this is what I tried :

f = @(t,y)(m*yn' + c*yn + k*yo - F0*sin(w*t));

a = 0;

b = 10;

n = 100;

h = (b-a)/n;

T = a:h:b;

F0 = 0;

w = 0;

m = 4;

k = 10;

c = 0.2;

y0 = 4;

[t,y] = myHeun(y0,a,b,f,n);

plot(t,y,'k')

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Anas Gharsa 2022-1-27

I even tried something like this :

f = @(t,y)(m*yn' + c*yn + k*yo - F0*sin(w*t));

a = 0;

b = 10;

n = 100;

h = (b-a)/n;

T = a:h:b;

F0 = 0;

w = 0;

m = 4;

k = 10;

c = 0.2;

y0 = 4;

h=(b-a)/n; %h=(b-a)/n

t=a:h:b;

u=y0*ones(1,n+1); %initial condition

for i=1:n

fi=feval(f,t(i),u(i)); %evaluation of f at t_i, u_i

u0=u(i)+h*fi; %application of Euler method to obtain u_{i+1}^0

u(i+1)=u(i)+h*(fi+feval(f,t(i+1),u0))/2; %application of Heun method

end

plot(t,y,'k')

and i get this error message:

Error in ex7>@(t,y)(m*yn'+c*yn+k*yo-F0*sin(w*t)) (line 3)

f = @(t,y)(m*yn' + c*yn + k*yo - F0*sin(w*t));

Error in ex7 (line 21)

fi=feval(f,t(i),u(i)); %evaluation of f at t_i, u_i

Torsten 2022-1-27

What is yo ?

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采纳的回答

VBBV 2022-1-27

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1637425-trying-to-use-heun-s-method-to-solve-an-ode#answer_883055

编辑：VBBV 2022-1-27

在 MATLAB Online 中打开

a = 0;
b = 10;
n = 100;
h = (b-a)/n;
% T = a:h:b;
F0 = 0;
w = 0;
m = 4;
k = 10;
c = 0.2;
y0 = 4;
h=(b-a)/n;                                                     %h=(b-a)/n
t=a:h:b;
u=y0*ones(1,n+1);       
f = @(t,y)(m*y + c*y + k*y0 - F0*sin(w*t));%initial condition
for i=1:n-1  
    fi=feval(f,t(i),u(i));                                      %evaluation of f at t_i, u_i
    u0=u(i)+h*fi;                                              %application of Euler method to obtain u_{i+1}^0
    u(i+1)=u(i)+h*(fi+feval(f,t(i+1),u0))/2;        %application of Heun method
end
plot(t,u,'k')

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Torsten 2022-1-27

You wrote you want to learn Matlab, and this is fine.

But since you got your problems as exercises for your homework, you should be able to state them properly.

And everybody in the forum is willing to help if you show that you spent some effort to solve the problem on your own. But did you really spend this effort ? Since the Heun program can't be written on your own if you don't know how to use it.

Anas Gharsa 2022-1-27

Dear Torsten, you got right to say that since you really don't know how much time i spend on this. I am not asking to risolve the exercises for me I am just asking some advices that would help me and may be guidance to the right direction!! and like i said it befor i am new to matlab and i am doing my best to learn it !! and for the Heun algorithm i did what i could after reading thounsands of pages that speaks of numerical solutions and reading many others scripts!! you can say everything you want but you can't tell me that i did nothing to try it by my self

by the way thank you for trying to help and thank you so much VBBV

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