Discrepancy with easy ODE.
2 vues (au cours des 30 derniers jours)
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Bobby Fischer
le 14 Jan 2021
Commenté : Bobby Fischer
le 14 Jan 2021
Hello, don't know why the discrepancy.
function fcno
y0=linspace(0,2,20);
t0=linspace(0,3,100);
figure(1)
close(1)
figure(1)
options=odeset('RelTol',1e-5);
subplot(1,3,1)
hold on
for k=1:20
[t,y]=ode45(@fun,t0,y0(k),options);
plot(t,y,'b')
end
title('ode')
subplot(1,3,2)
hold on
t=t0;
for k=1:20
f2=y0(k)*exp(t)./(1+(exp(t)-1)*y0(k));
plot(t,f2,'r')
end
title('solution')
%%
lon=101;
t=linspace(0,3,lon);
h=3/(lon-1);
y0=linspace(0,2,20);
subplot(1,3,3)
hold on
for m=1:20
y=zeros(1,lon);
y(1)=y0(m);
for k=1:100
y(k+1)=y(k)+h*y(k)*(1-y(k));
end
plot(t,y,'g')
end
plot([0 3],[0 0],'m--','linewidth',3)
plot([0 3],[1 1],'m--','linewidth',3)
title('my ode')
%%
function [t,yp]=fun(t,y)
yp=y*(1-y);
end
end
2 commentaires
Mischa Kim
le 14 Jan 2021
Hi Bobby, can you please provide more information of what you are trying to accomplish and the (unexpected) results you receive?
Réponse acceptée
J. Alex Lee
le 14 Jan 2021
You have a syntax error on what your odefun is returning. To fix:
function [yp]=fun(t,y)
yp=y*(1-y);
end
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