Why do I get the error 'The number of inputs and outputs of the model must match that of the data.'?

I am attempting to run a nonlinear grey box estimation on a defined ODE function, and I keep recieving the same error, no matter what I change. I don't see where the problem comes from. I have tried to change the input, but that has not worked. Here are the three files:

%6-11-19
%u = [u0*sin(w*t); u0*w*cos(w*t)];
function [dx, y] = DOF1damped(t, x, u, w, u0, m, k, c)

y = [x(1);x(2)];
dx = [x(2) ;((-k/m).*x(1) - (c/m).*x(2) + (k/m).*(u0*sin(w*t)) + (c/m).*(u0*w*cos(w*t)))];
end

_

%6-12-19

clear 
close all
clc



u0 = 1; %amplitude ()
w = 1; %hz
m = 0.85048569375; %kg
k = 356.9085; % N/m
c = 10; %N/m*s
tspan = [0 10];
t = [0:.1:10];
u = [u0*sin(w*t); u0*w*cos(w*t)];


x0 = [0;0];
[t, x] = ode45(@(t,x)DOF1damped(t, x, u, w, u0, m, k, c), tspan, x0); 

data = iddata(x, t, .1);

plot(t, x)

_

filename = 'DOF1damped';
Order = [2 0 2];

u0 = 1; %amplitude ()
w = 1; %hz
m = 0.85048569375; %kg
k = 356.9085; % N/m
c = 10; %N/m*s

Parameters = {u0,w,m,k,c};
InitialStates = [0; 0];
Ts = 0;


nlgr = idnlgrey(filename, Order, Parameters, InitialStates, Ts, 'Name','DOF1grey');

nlgr = setinit(nlgr, 'Fixed', {false false}); % Estimate the initial states.
setpar(nlgr,'Fixed',{true true true true false});
opt = nlgreyestOptions('Display', 'on');

nlgr = nlgreyest(data,nlgr,'Display','Full');
c_est = nlgr.Parameters(5).Value;
[nonlinear_c_est, dnonlinear_c_est] = getpvec(nlgr,'free')


compare(data,nlgr)

Thanks for any help

[Stephen23]

@Ben Trinkle: please show the complete error message. This means all of the red text.

[Ben25]

Here's the full error

>> DOF1grey

Error using iddata/nlgreyest (line 59)

The number of inputs and outputs of the model must match that of the data.

Error in DOF1grey (line 21)

nlgr = nlgreyest(data,nlgr,'Display','Full');

[Omar]

Hey @Ben25 I'm having the same issue, did you find a solution?

[Omar]

Figured it out, In my case, my iddata object had only one output, and the equation was outputting 2 variables, and I have defined the order as [2 1 2]

once I updated the ODE to output only one variable, and the order to be [1 1 2] the error disappeared.

Answer 1

[Cris LaPierre]

You define iddata as 2 output (y = 597x2) and 1 input (t = 597x1).

Your model nlgr is defined as having order [2 0 2], which corresponds to the number of model outputs, inputs, and states. This must match the output and input size of iddata.

Change order to [2 1 2] to resolve the error,