How to correct "Undefined function 'mtimes' for input arguments of type 'cell'."

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I am trying to estimate parameters of some ODEs that describe the velocity vector of a wheeled mobile robot using the system identification toolbox. Specifically, I am trying to solve a non linear grey box model to find these parameters.
When I run the model I get the following error:
Error using iddata/nlgreyest
Error or mismatch in the specified ODE file "threewheeledomni_modelFile."
The error message is: "Undefined function 'mtimes' for input arguments of type 'cell'."
Here is the code for the ODE, the other file is too much to copy in here:
function[dx,y] = threewheelomni_modelFile(t,x,u,alpha1,alpha2,alpha3,beta1,beta2,beta3,gamma1,gamma2,gamma3,l,r,varargin)
beta =[beta1,beta2,beta3];
rotMat = [cos(x(3)),-sin(x(3)),0;sin(x(3)),cos(theta0),0;0,0,1];
J1 = [sin(alpha(1)+beta(1)+gamma(1)),-cos(alpha(1)+beta(1)+gamma(1)),-l*cos(beta(1)+gamma(1));...
J2 = [r*cos(gamma1),0,0;0,r*cos(gamma2),0;0,0,r*cos(gamma3)];
dx = inv(rotMat)*inv(J1)*J2*u;
Richard Westgarth
Richard Westgarth on 21 Nov 2022
Correct. Im saying that was a mistake on my part. theta0 shouldnt have been a fixed parameter, its a variable. I updated the code such that theta0 is calculated from an integral function of x(3) now I'm rolling along ok. Its also possible I attached mismatched files. Thanks for the response, you helped me solve this one by highlighting that detail.

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Accepted Answer

Walter Roberson
Walter Roberson on 21 Nov 2022
The mlx constructs 11 parameters starting from alpha1 . However the modelFile expects 12 parameters starting from theta0
  1 Comment
Richard Westgarth
Richard Westgarth on 21 Nov 2022
theta0 should have been the 3rd element of the state vector. Silly question, sorry about that.

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