Help!!! Mysterious FSOLVE InputOutputModel/vertcat Error!

I'm new to MATLAB and I keep getting this error when I try to solve a system of 10 equations in 10 unknowns:

Error using InputOutputModel/vertcat (line 48)
In "[M1;M2]", M1 and M2 must have the same number of
inputs/columns.

Error in fpiss_fun (line 25)
f = [

Error in @(x)fpiss_fun(x,param)

Error in fsolve (line 218)
            fuser = feval(funfcn{3},x,varargin{:});

Error in Sample (line 14)
x=fsolve(f,x0)

Caused by:
    Failure in initial user-supplied objective function
    evaluation. FSOLVE cannot continue.

Relevant code:

clear all;
clc;
param = fpi_parameters;
options = optimoptions('fsolve','Display','iter');
x0 = [2.1;1.8;.95;12;9;10;.01;.16;.001;3];
f=@(x)fpiss_fun(x,param);
x=fsolve(f,x0)

___________

function param = fpi_parameters()

param.bet = .99;   
param.ak = .005;    
param.an = .05;   
param.lamk = .01;  
param.lamn = .1;    
param.epk = .5;     
param.epn = .6;     
param.dele = .02;   
param.delu = .01;   
param.chik = 1;     
param.chin = 1;     
param.alph = .3;    
param.zss =1;
param.wss =1.45;
param.rss =0.04;

______________

function f = fpiss_fun(x,param)

%Allows referencing parameters by fieldnames instead of param.fieldname
nms = fieldnames(param);
for j = 1:length(nms)
    eval([nms{j} '='  'param.' nms{j} ';'])
end

%Renaming endogenous variables
y=x(1);
c=x(2);
l=x(3);
n=x(4);
ke=x(5);
ku=x(6);
vk=x(7);
vn=x(8);
thetk=x(9);
thetn=x(10);

%Declaring the system to be solved for (y c l n ke ku vk vn thetk thetn)
f = [
    wss*n+rss*ke+lamk*(1-dele)*ke+ku-c-l;
    y-zss*n^(alph)*ke^(1-alph);
    ke-(1-dele)*(1-lamk)*ke-chik*thetk^(epk)*l;
    ku-(1-chik*thetk^(epk))*(1-delu)*l;
    n-(1-lamn)*n-chin*thetn^(epn)*(1-n);
    ak/(chik*thetk^(epk-1))-bet*(zss*(1-alph)*n^alph*ke^(-alph)-rss+(1-lamk)*(1-dele)*ak/(chik*thetk^(epk-1)));
    an/(chin*thetn^(epn-1))-bet*(zss*alph*n^(alph-1)*ke^(1-alph)-wss+(1-lamn)*an/(chin*thetn^(epn-1)));
    thetn-vn/(1-n);
    thetk-vk/l;
    (1-(1-chik*thetk^(epk))*(1-delu)*bet)/(chik*thetk^(epk))*(1-bet*(1-dele)*(1-lamk))-bet*(rss+lamk*(1-dele))
    ];

Any ideas why this isn't working? Thanks!!!

[Alan Weiss]

Please edit your post using the {}Code tool as appropriate so we can read it.

Alan Weiss

MATLAB mathematical toolbox documentation

Answer 1

[Walter Roberson]

Notice that the error is said to occur at InputOutputModel/vertcat instead of at vertcat . If you were using the normal vertcat, the message would say

Error using vertcat
Dimensions of matrices being concatenated are not consistent.

This suggests that in a directory named InputOutputModel that is on your MATLAB path, there is a vertcat.m routine that is being called instead of the built-in vertcat routine. You will need to remove the directory InputOutputModel from your MATLAB path, or else you will need to recode the vertcat there to be type-specific so that it is not found while matlab is searching for its vertcat routine. "vertcat" is the 'real' name of the operation carried out when you use a semi-colon inside []

[a b;c d]

is turned into calls to

vertcat( horzcat(a,b), horzcat(c, d) );

Is it possible you are running this code within Simulink ?

[Walter Roberson]

It turns out that InputOutputModel is used for transfer functions and state-space models.

[Biplob Chowdhury]

Hi,

I am in the same problem using MATLAB R2019b while simulating a Wind Turbine model. I need to define a state matrix. The state matrix is like this:

Ar = [Aa+Ba*Kx-Lx*Ca, Bda*Theta_dac+Ba*Kd, Ba*Ki; zeros(nxd,nxa)-Ld*Ca, F_dac, zeros(nxd,ni); 0, 0, 0];

The error message is:

Error using InputOutputModel/vertcat (line 47)

In "[M1;M2]", M1 and M2 must have the same number of inputs/columns.

Error in DAC (line 236)

Ar = [Aa+Ba*Kx-Lx*Ca, Bda*Theta_dac+Ba*Kd, Ba*Ki; zeros(nxd,nxa)-Ld*Ca, F_dac, zeros(nxd,ni); 0, 0,

0];

I have checked all the individual elements, the “Ba*Ki” gives a message like this:

ans =

Generalized matrix with 14 rows, 1 columns, and the following blocks:

Ki: Parametric 3x1 matrix, 1 occurrences.

Type "double(ans)" to see the current value, "get(ans)" to see all properties, and "ans.Blocks" to interact with the blocks.

I have already checked, and the ‘InputOutputModel’ is not in the MATLAB path.

I would appreciate any help on this.

Best regards

Answer 2

[Alan Weiss]

I am not sure what your code does. Can you please try to execute

 testvalue = fpiss_fun(x0,param)

where x0 is your initial point? Do you get a result testvalue?

Alan Weiss

MATLAB mathematical toolbox documentation