# trying to use heun's method to solve an ode

7 visualizzazioni (ultimi 30 giorni)
Anas Gharsa il 27 Gen 2022
Modificato: Torsten il 28 Gen 2022
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')
##### 5 CommentiMostra 3 commenti meno recentiNascondi 3 commenti meno recenti
Anas Gharsa il 27 Gen 2022
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 il 27 Gen 2022
What is yo ?

Accedi per commentare.

### Risposta accettata

VBBV il 27 Gen 2022
Modificato: VBBV il 27 Gen 2022
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')
##### 8 CommentiMostra 6 commenti meno recentiNascondi 6 commenti meno recenti
Torsten il 27 Gen 2022
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 il 27 Gen 2022
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

Accedi per commentare.

### Categorie

Scopri di più su Programming in Help Center e File Exchange

R2021b

### Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!

Translated by