Running a MATLAB script in Python: "Operator '*' is not supported for operands of type 'cell'."

I am trying to run a MATLAB script in Python to generate a trajectory for the Lorenz system. My Python code is:

import matlab.engine

eng = matlab.engine.start_matlab()
traj = eng.gen_lorenz([1, 1, 1],10,8/3,28,250,1/50)

eng.quit()

print(traj)

My MATLAB function is:

function [output] = gen_lorenz(init_pos,sigma,beta,rho,tf,dt)
%GEN_LORENZ 
%Generates Lorenz Trajectory based on initial position (init_pos),
%sig/rho/beta values, every dt seconds to a final time (tf)

f = @(t,a) [-sigma*a(1) + sigma*a(2);
            rho*a(1) - a(2) - a(1)*a(3);
            -beta*a(3) + a(1)*a(2)];
[~,a] = ode45(f,[double(0):dt:double(tf)], init_pos);

output = a;
end

When I run the code, I keep getting the error "Operator '*' is not supported for operands of type 'cell'" on the line: f = @(t,a) ...

I'm assuming it's a problem with trajectory array (a) or the sig/beta/rho constants, but I'm not sure why they're being interpreted as a cells. The function works fine if it's run just on MATLAB.

Thanks

[Hanjin Liu]

Hello.

Be sure that list objects in Python are converted to cells in matlab.engine so [1, 1, 1] is interpreted as a cell {1, 1, 1}.

You need to import matlab.double and the correct code will look like:

eng.gen_lorenz(matlab.double([1, 1, 1]), ...).

[Max Van der Velden]

Ok, after doing @Hanjin Liu's suggestions, I am getting the error:

ValueError: initializer must be a rectangular nested sequence

with the new line:

traj = eng.gen_lorenz(initial_pos,matlab.double(10),matlab.double(8/3),matlab.double(28),matlab.double(250),matlab.double(0.02))

Thanks for the help.

[Hanjin Liu]

The following code worked well in my PC with a copy of your MATLAB function.

from matlab import double
traj = eng.gen_lorenz(double([1, 1, 1]),10.0,8/3,28.0,250.0,1/50)

You got a ValueError because matlab.double only takes arguments that are iterable.

matlab.double(10) ... error.

matlab.double([10]) ... works, but 10.0 is simpler because float in Python will be automatically converted to MATLAB double.

[Max Van der Velden]

Ok, I see why that works. Thank you for the help!