"Unable to perform assignment because the size of the left side is 1-by-1 and the size of the right side is 0-by-0."

I'm trying to run a CR3BP script. It keeps saying that dS(4,1) is a 1 by 1 and and the right side of the equation is 0 by 0. I can't figure out why:

function [dS] = CR3BP(~, s, mu, ~)

% Initialize state at input epoch t.

dS = zeros(6,1);

% Retrieve components from current state.

x = s(1,1);

y = s(2,1);

z = s(3,1);

vx = s(4,1);

vy = s(5,1);

vz = s(6,1);

% Compute the distance from the smaller primary.

r_1 = sqrt((x + mu - 1)^2 + y^2 + z^2);

% Compute the distance from the larger primary.

r_2 = sqrt((x + mu)^2 + y^2 + z^2);

% Assign velocities along x, y and z axes of the CR3BP rotating-frame.

dS(1,1) = vx;

dS(2,1) = vy;

dS(3,1) = vz;

% Assign accelerations along x, y and z axes of the CR3BP rotating-frame,

% using equations of motion from the CR3BP model.

dS(4,1) = x + 2*vy - (1 - mu)*(x + mu)/(r_2^3) - ...

mu*(x - 1 + mu)/(r_1^3);

dS(5,1) = y - 2*vx - ((1 - mu)*y)/(r_2^3) - (mu*y)/(r_1^3);

dS(6,1) = -((1 - mu)*z)/(r_2^3) - (mu*z)/(r_1^3);

end

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ERROR below:

Unable to perform assignment because the size of the

left side is 1-by-1 and the size of the right side is

0-by-0.

Error in CR3BP (line 35)

dS(4,1) = x + 2*vy - (1 - mu)*(x + mu)/(r_2^3) - ...

Error in odearguments (line 92)

f0 = ode(t0,y0,args{:}); % ODE15I sets args{1} to yp0.

Error in ode45 (line 107)

odearguments(odeIsFuncHandle,odeTreatAsMFile, solver_name, ode, tspan, y0, options, varargin);

Error in Single_Shooting_Lyapunov_Main (line 49)

[t_cor, s_cor] = ode45('CR3BP', cor_tspan, cor_xinit, options);

Answer 1

[Walter Roberson]

I predict that your mu is empty.

function [dS] = CR3BP(~, s, mu, ~)

That function expects 4 parameters.

[t_cor, s_cor] = ode45('CR3BP', cor_tspan, cor_xinit, options);

That syntax is going to call CR3BP with two parameters. I am a bit surprised that you do not get an error in CR3BP about not passing enough arguments.

In order to pass extra parameters to your function you should be using a function handle and parameterize it: http://www.mathworks.com/help/matlab/math/parameterizing-functions.html

[Mark Munson]

Thank you!

Your premonition that mu was empty was correct. It now works.