I got two different graphs from my code like ODE89 and Eulers method. I need to compare the graphs in it.

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Naveen Krish
Naveen Krish 2022-3-14
评论： Naveen Krish 2022-3-18
ODE89
clc
clear all
A0=1;
B0=3;
P0=0;
K=5*10^-5;
Yb=1;
Yp=0.15;
tspan = [0 43200];
[t,Y] = ode89(@(t,Y) odefun(t,Y, K, Yb, Yp),tspan, [A0;B0;P0]);
figure (1)
plot(t,Y(:,1))
figure (2)
plot(t,Y(:,2))
figure (3)
plot(t,Y(:,3))
function dYdt = odefun(t,Y,K,Yb,Yp)
dYdt = [(-K*Y(1)*Y(2));
(-Yb*(K*Y(1)*Y(2)));
(Yp*(K*Y(1)*Y(2)))];
end
Eulers
nsteps = 12;
t = zeros (nsteps,1);
A = zeros (nsteps,1);
B = zeros(nsteps, 1);
P = zeros(nsteps,1);
A(1) = 1;
B(1) = 3;
C(1) = 0;
K = 5*10^-5
for k = 2:13
t(k) = t(k-1)+3600
A(k) = A(k-1)+(-K*A(k-1)*B(k-1))*3600;
B(k) = B(k-1)+(-Yb*(K*A(k-1)*B(k-1)))*3600;
P(k)= P(k-1)+ Yp*(K*A(k-1)*B(k-1))*3600;
end
plot (t,A)
figure (1)
plot(t,A(:,1))
plot (t,B)
figure (2)
plot(t,B(:,1))
plot(t,P)
figure (3)
plot(t,P(:,1))
I need to compare the ODE89 graph of A,B and P with Euler's A,B and P

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采纳的回答

Davide Masiello
Davide Masiello 2022-3-15
编辑：Davide Masiello 2022-3-15
Ran in:
clc
clear all
%% ODE89
A0=1;
B0=3;
P0=0;
K=5*10^-5;
Yb=1;
Yp=0.15;
tspan = [0 43200];
[x,Y] = ode89(@(t,Y) odefun(t,Y, K, Yb, Yp),tspan, [A0;B0;P0]);
%% Euler
nsteps = 12;
t = zeros (nsteps,1);
A = zeros (nsteps,1);
B = zeros(nsteps, 1);
P = zeros(nsteps,1);
A(1) = 1;
B(1) = 3;
C(1) = 0;
K = 5*10^-5;
for k = 2:13
t(k) = t(k-1)+3600;
A(k) = A(k-1)+(-K*A(k-1)*B(k-1))*3600;
B(k) = B(k-1)+(-Yb*(K*A(k-1)*B(k-1)))*3600;
P(k)= P(k-1)+ Yp*(K*A(k-1)*B(k-1))*3600;
end
figure(1)
subplot(1,3,1)
plot (t,A,x,Y(:,1))
xlabel('t')
ylabel('A')
subplot(1,3,2)
plot (t,B,x,Y(:,2))
xlabel('t')
ylabel('B')
subplot(1,3,3)
plot(t,C,x,Y(:,3))
xlabel('t')
ylabel('P')
legend('ODE89','Euler','Location','Best')
function dYdt = odefun(t,Y,K,Yb,Yp)
dYdt = [(-K*Y(1)*Y(2));
(-Yb*(K*Y(1)*Y(2)));
(Yp*(K*Y(1)*Y(2)))];
end
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