MATLAB: Undefined function or method ‘V’ for input arguments of type ‘double’.

errorundefined function or method

Hi There. I'm getting the following error when I try to run this programme. *Undefined function or method 'V' for input arguments of type 'double'.*
     %Mesures=importdata('C:\Users\wrd\Documents\Données du moteur\AR-Variat charge _(ess2-01-07)\D1500_20%.dat');
     Mesures=importdata('C:\Users\wrd\Documents\Données du moteur\AR-Variat charge _(ess2-01-07)\D1500_20%.dat');
     thet=Mesures(:,1);
     %theta=thet;
     theta=Mesures(1:5:numel(thet),1);
           %Pres=10^5*Mesures(1:numel(theta),2); 
     P=10^5*Mesures(1:5:numel(thet),2); 
         %dPthet=gradient(P,theta);   %dPthet=10^5*Mesures(:,2);
         % P(1)=Pres(1); P(2)=Pres(2); P(numel(theta))=Pres(numel(theta)); P(numel(theta)-1)=Pres(numel(theta)-1);
          %    for i=3:(numel(theta)-2)
           %        P(i)=(Pres(i-2)+Pres(i-1)+Pres(i)+Pres(i+1)+Pres(i+1))/5;
            %  end 
       dPtheta=gradient(P,theta); 
     %débit d'air
     dVN=40;      %[Nm3/h]
     r=300;
     Pad=100000;
     Tad=273.15;
     dm=(dVN*Pad)/(r*Tad*3600);                                    %[Kg/s]
    m=(dm*60)/(2*N);
   % m=6*10^(-4);
    %stop
  Qcumul=zeros(numel(P),1);
   % Angle de début et bde fin de calcul du dégagement de chaleur
   AngPMH_comp=0;   %***TRES IMPORTANT : Si le cycle commence de 0 prendre 360 si il commence de -360 prendre 0
   thetmax=AngPMH_comp+70;   
for i=2:numel(theta)     
                     %Calcul du volume et de sa dérivée
                     clear V
                     [VL(i),dVthet(i)]=V(theta(i),Cu,Vm,Landav);            
end
%plot(theta,dPtheta); plot(theta,dQthet_app,'r'); axis([AngPMH_comp-20 thetmax -10 60]);grid on;hold on;

Best Answer

One would have no idea what you expected from this code. MATLAB certainly had no idea.
READ THE ERROR MESSAGE. It points out that V is undefined. In fact, inside a loop, you use the function or variable V.
clear V
[VL(i),dVthet(i)]=V(theta(i),Cu,Vm,Landav);
Even worse, on the very line before you try to use V, you clear it!
If you want to use V as a function or variable, it needs to exist. If not, then MATLAB will (and should) throw up its virtual hands and give up the ghost.
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