there are two coupled differential equation, I try to solve that differential for the i = 1 to 5, but i think my for loop is incorrect.

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these are the differential equation I want to solve where the i = 1 to 5
I want to solve these differential equation but maybe the loop isn't correct or we can't apply loop here?
clc
ti = 0;
tf = 10E-6;
tspan = [ti tf];
a = 0.6;
n = 0.05;
tc = 10E-9;
r = 1.5;
F = 1;
k =1:1:5;
f = zeros(length(k),1) ;
for i = 1:length(k)
y(1) = A(i)
y(2) = O(i)
f = @(t,y) [
(-1/(2*tc)).*(1 - r/(1+ (A(i)^2)./F)).*A(i) + (n/(2*tc)).*((cos(O(i+1)- O(i))).*A(i+1) + (cos(O(i+1)- O(i))).*A(i-1)) ;
(a./(2*tc)).*(r/(1 + (A(i)^2)./F)) + (n/(2*tc)).*((A(i+1)./A(i)).*sin(O(i+1) - O(i)) - (A(i-1)./A(i)).*sin(O(i-1) - O(i)));
O(i+1) - O(i)
];
end
Unrecognized function or variable 'A'.
[time,Y] = ode45(f,tspan,[0;0;0]);
plot(time,Y(:,3))
  5 个评论
SAHIL SAHOO
SAHIL SAHOO 2022-8-1
these are the equation that I want to solve by using ode45, where i = 1 to 5.
conditions A0 =0 and Ψ0 = 0 and whenever the i+1>=5 then (( i+1) - 5), means the A6 will be A1, A7 will be A2,
Ψ6 = Ψ1 and Ψ7 = Ψ2.
its like a circle i = 1 2 3 4 5 6 7
A1 A2 A3 A4 A5 A1A2....

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回答(1 个)

Walter Roberson
Walter Roberson 2022-7-31
Note that because you use A(i+1) and O(i-1) you cannot produce plots for the first or last entries in A or O.
%number of data points
N = 5;
%put in your real A and O data here!!
A = randn(1,N);
O = rand(1,N) * 10;
%process data
ti = 0;
tf = 10E-6;
tspan = [ti tf];
a = 0.6;
n = 0.05;
tc = 10E-9;
r = 1.5;
F = 1;
k = 1:N;
f = zeros(N,1) ;
for i = 2:N-1
f = @(t,y) [
(-1/(2*tc)).*(1 - r/(1+ (A(i)^2)./F)).*A(i) + (n/(2*tc)).*((cos(O(i+1)- O(i))).*A(i+1) + (cos(O(i+1)- O(i))).*A(i-1)) ;
(a./(2*tc)).*(r/(1 + (A(i)^2)./F)) + (n/(2*tc)).*((A(i+1)./A(i)).*sin(O(i+1) - O(i)) - (A(i-1)./A(i)).*sin(O(i-1) - O(i)));
O(i+1) - O(i)
];
[time,Y] = ode45(f,tspan,[0;0;0]);
plot(time, Y(:,3), 'DisplayName', "i = " + i);
hold on
end
legend show
  5 个评论
Walter Roberson
Walter Roberson 2022-7-31
Note that once you have the definitions for the boundary ode, my recommendation would be to use the symbolic toolbox to set up the entire system of 15 coupled equations at the same time. Then follow the first example in the document for odeFunction() to convert to something that can be used with ode45

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