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# why plots are not matching with ode

2 visualizaciones (últimos 30 días)
shiv gaur el 12 de Mzo. de 2022
Cerrada: Jan el 12 de Mzo. de 2022
% Set parameters
Tstart = 0.0;
Tend = 200.0;
Nt = 200000;
dT = (Tend-Tstart)/Nt;
X0 = 1;
Y0 = 1;
Z0 = 0;
N = 20;
SIGMA = 0.2;
R = 0.2;
B = 5.7;
%
% Initialize coefficient arrays
T = zeros(Nt+1,1);
X = zeros(Nt+1,1);
Y = zeros(Nt+1,1);
Z = zeros(Nt+1,1);
a = zeros(N+1,1);
b = zeros(N+1,1);
c = zeros(N+1,1);
T(1) = 0.0;
X(1) = X0;
Y(1) = Y0;
Z(1) = Z0;
for j = 2:Nt+1
a(1) = X(j-1);
b(1) = Y(j-1);
c(1) = Z(j-1);
for k = 1:N
SB = 0.0;
for i= 0:k-1
SB = SB + a(i+1)*c(k-i);
end
a(k+1) = ((-b(k) - a(k)))/k+1;
b(k+1) = ((a(k) +R*b(k)))/k+1 ;
c(k+1) =( SIGMA-B*c(k) + SB)/k+1 ;
end
x = a(1);
y = b(1);
z = c(1);
for k = 2:N+1
x = x + a(k)*dT^(k-1);
y = y + b(k)*dT^(k-1);
z = z + c(k)*dT^(k-1);
end
T(j) = T(j-1) + dT;
X(j) = x;
Y(j) = y;
Z(j) = z;
end
figure(1)
plot(T,X,'Color','red')
hold on
figure(2)
plot(T,Y,'Color','red')
hold on
figure(3)
plot(T,Z,'Color','red')
hold on
figure(4)
plot3(X,Y,Z,'Color','red')
hold on
%matching with ode
function kk2
close all; clear all;
% accuracy
%options = odeset('RelTol',1e-9,'AbsTol', 1e-16);
a=0.2;
b=0.2;
k=5.7;
[t,y]=ode45(@f,[0 200],[1;1;0.05] );
%plot(t,y(:,2),t,y(:,4),t,y(:,6))
%
plot(t,y(:,1),t,y(:,2),t,y(:,3))
xlabel('t');
ylabel('x,y,z')
%plot3(y(:,1),y(2,:),y(:,3))
function dy=f(t,y)
a=0.2;
b=0.2;
k=5.7;
dy=[(-y(2)-y(3));y(1)+a*y(2);b+y(3)*(y(1)-k)];
end
end
what is the problem above program
##### 3 comentariosMostrar 1 comentario más antiguoOcultar 1 comentario más antiguo
shiv gaur el 12 de Mzo. de 2022
irritating some one who are not able to answer the question he select the choice of closing the question with out giving answer the question this is not simple problem
Jan el 12 de Mzo. de 2022
Your question does not contain enough information to be answered. You state, that the "plots do not match the ODE", but of course the diagrams are the results of the equations. As said already, there is no chance to guess, why you expect different results, because you do not mention any reason.
Re-opening your question without adding any further useful details is a misusage of the forum. Stop this.

R2021b

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