I have a problem with this ode45

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fartash2020
fartash2020 2019-1-31
评论： Star Strider 2019-1-31
Hi Matlab Users,
I cannot understand what is wrong with my code. I would appreciate if anyone could help me.
I got this error:
Index in position 1 is invalid. Array indices must be positive integers or logical values.
% Define model parameters: d, Lambda, DeltaE, V, Om, kappa
clear; clc;
DeltaE = 0;
Lambda = 1e-1;
d = 12;
kappa = 1;
Ksi = 5e-5; % damping parameter
Om = 1e-2; % driving frequency
%V = 9.2e-3; % driving amplitude
V = 9e-4;
tspan=[0:1e5];
% Define the function with integration variables
fun_ode = @(t, y) shapiro(t,y,d,DeltaE,Lambda,V,Om,kappa);
% fun_shapiro is a function which contains th coupled differential equations of the driven undamped soliton-surface plasmon Josephson junction with asymmetric coupling. You need to code this.
% Integrator options
options = odeset('RelTol',1e-7,'AbsTol',[1e-8 1e-8]);
%Define time array in integer multiples of 2*pi/Om
t = 2*pi/Om*(1:200);
%Define a set of initial points Phi0,Z0. A coarse example is the following:
[Phi0,Z0] = meshgrid(-1:0.4:1,-1:0.4:1);
% initialize the phase space figure
figure(1),clf;
axis([-1.5 1 -0.3 0.3]);
grid on;
hold on;
% Integrate the system from each initial point and plot the results
[T, Y]=ode45(fun_ode,tspan,[Phi0(i,j) Z0(i,j)],options);
% Collapse the Phi values into the [-1,1] range.
Y(:,1) = wrapToPi(Y(:,1)*pi)./pi;
plot(Y(:,1),Y(:,2),'.k','MarkerSize',3);
% plot the same values displaced by 2*pi. This is just for a better looking figure:
hold on;
plot(Y(:,1)-2,Y(:,2),'.k','MarkerSize',3);
and this is shapiro function
function dydt = shapiro(t,y,DeltaE,Lambda,d,kappa,Ksi,Om,V)
dydt = zeros(2,1);
qc = fun_q(Lambda,d,y(2));
a = sqrt((1-y(2))./(1+y(2)));
dydt(1) = (DeltaE + Lambda.*y(2) - 0.5*(a.*kappa - 1./a)...
*qc.*cos(pi*y(1)) + V*cos(t))/(Om*pi);
dydt(2) = -.5*sqrt((1-y(2))*(1+y(2)))*qc*(1+kappa)...
*sin(pi*y(1))/Om - Ksi*pi*dydt(1);
end
in addition to that
function q = fun_q(Lambda,d,Z)
q = sqrt(.5*(1+Z))*exp(-d*sqrt(2*Lambda*(1+Z)));
%q = 1.d-5; % Constant q for BEC-Josephson model
end
With my regards,
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fartash2020
fartash2020 2019-1-31
I would highly appreciate if you could you give the link to that?
madhan ravi
madhan ravi 2019-1-31
respond to James answer below

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采纳的回答

Star Strider
Star Strider 2019-1-31
Could the problem be in or related to ‘fun_q’ that you have not posted?
It would likely help if you posted it.
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fartash2020
fartash2020 2019-1-31
I fixed the code and I got the plots, thank you all

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更多回答（1 个）

James Tursa
James Tursa 2019-1-31
I don't see anywhere in your code where you define i and j before using them as indexes into Phi0 and Z0, so they default to the imaginary numbers, hence the error. Perhaps you intended to wrap all of this in for loops?
  2 个评论
fartash2020
fartash2020 2019-1-31
yes your are right, but even if I choose any random i and j this does not work. lets set them 1 and 1 respectively. Maybe there is something wrong with the shapiro function that I have written,
James Tursa
James Tursa 2019-1-31
Are you saying that if you set i=1 and j=1 just prior to the line in question, that you get the exact same error? Or do you get a different error?

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