Error: "Dot indexing is not supported for variables of this type.'' Class structure.

Hello everyone! I´m coding a program to design a turbine from several input data. I use a class variable for this purpose. One of the properties ("trapecio") is another class variable. When I run the code it shows me an error saying "Dot indexing is not supported for variables of this type".

One day the code runned perfectly, but the following day it did not.

Any help will be apreciated, thanks in advance!

Here it´s the code:

classdef diseno 
    properties 
        m=0
        n=0
        T0_e=0
        p0_e=0
        h0_e=0
        s0_e=0
        p_s=0
        wi=0;
        P_int=0
        P_ef=0
        eta_tt=0
        eta_te=0
        T_s=0
        T_ss=0
        h_ss=0
        h_s=0
        s_s=0
        c_s=0
        Cp=0
        gamma=0
        trapecio=trapecio(0,0,0,0,0,0)
    
        bidimensional=false
        supersonico=false
        
    end
    methods
        function d=diseno(m,T0_e,p0_e,p_s,n,PSI,PHI,GR,Cp,gamma,i_r,i_e)
            if(m>0 && T0_e>0 && p0_e>0 && p_s>0 && n>0 && PSI>0 && PHI>0)
                d.m=m;
                d.n=n;
                d.T0_e=T0_e;
                d.p0_e=p0_e;
                d.h0_e=Cp*T0_e;
                d.s0_e=Cp*log(T0_e);
                d.p_s=p_s; 
                d.Cp=Cp;
                d.gamma=gamma;
                
                eta_te_prime=0; d.eta_te=0.7; iteracion_eta=0;
                d.wi=d.eta_te*d.Cp*d.T0_e*(1-(d.p_s/d.p0_e)^((d.gamma-1)/d.gamma));

                while(abs(eta_te_prime-d.eta_te)>0.00001 && iteracion_eta<100)
                    eta_te_prime=d.eta_te;

                   d.trapecio=trapecio(d,PSI,PHI,GR,i_r,i_e);

                   d.eta_te=d.wi/(d.wi+d.trapecio.zeta_e*d.trapecio.c1^2/2+d.trapecio.zeta_r*d.trapecio.w2^2/2+d.trapecio.c2^2/2+d.trapecio.Y_4r);

                    iteracion_eta=iteracion_eta+1;
                end
                d.wi=d.eta_te*d.Cp*d.T0_e*(1-(d.p_s/d.p0_e)^((d.gamma-1)/gamma));
                d.trapecio=trapecio(PSI,PHI,GR,d,i_r,i_e);
                d.eta_te=d.wi/(d.wi+d.trapecio.zeta_e*d.trapecio.c1^2/2+d.trapecio.zeta_r*d.trapecio.w2^2/2+d.trapecio.c2^2/2);
                d.eta_tt=d.wi/(d.wi+d.trapecio.zeta_e*d.trapecio.c1^2/2+d.trapecio.zeta_r*d.trapecio.w2^2/2);
                d.P_int=d.m*d.wi;
                d.P_ef=d.P_int*0.95;
                
              

            end

        end
    end
end

classdef trapecio 
    properties % Se va a suponer H/l(e)=1.5 y H/l(r)=1
     c1=0
     w1=0
     c2=0
     w2=0
     ca=0
     u=0
     delta_cu=0
     cu1=0
     cu2=0
     wu1=0
     wu2=0
     a1=0
     a2=0
     b1=0
     b2=0
     a1_prime=0
     a2_prime=0
     b1_prime=0
     b2_prime=0
     i_e=0
     i_r=0
     am=0
     bm=0
     epsilon_e=0
     epsilon_r=0
     delta_e=0
     delta_r=0
     calado_e=0
     calado_r=0
     sigma_e=0
     sigma_r=0
     theta_e=0
     theta_r=0
     Dm=0
     H0=0
     H1=0
     H2=0
     l_e=0
     l_r=0
     ze=0
     zr=0
     zeta_e=0
     zeta_r=0
     Y_e=0
     Y_r=0
     Y_4r=0
        
    end
    methods
        function t=trapecio(d,PSI,PHI,GR,i_r,i_e)
            
                t.u=sqrt(d.wi/PSI);
                t.ca=t.u*PHI;
                t.delta_cu=t.u*PSI;
                t.a2=atan((1-GR)/PHI+0.5*PSI/PHI);
                t.a1=atan((1-GR)/PHI-0.5*PSI/PHI);
                t.b2=atan(GR/PHI+0.5*PSI/PHI);
                t.b1=atan(GR/PHI-0.5*PSI/PHI);
                t.c1=t.ca/cos(t.a1);
                t.c2=t.ca/cos(t.a2);
                t.w1=t.ca/cos(t.b1);
                t.w2=t.ca/cos(t.b2);
                t.cu2=t.c2*sin(t.a2);
                t.cu1=t.c1*sin(t.a1);
                t.wu2=t.w2*sin(t.b2);
                t.wu1=t.w1*sin(t.b1);
                t.i_e=i_e;
                t.i_r=i_r;
                t.a2_prime=t.a2-t.i_e*pi/180;
                t.b1_prime=t.b1-t.i_r*pi/180;
                t.am=abs(atan((tan(t.a1)-tan(t.a2))/2));
                t.bm=abs(atan((tan(t.b1)-tan(t.b2))/2));
                t.epsilon_e=abs(t.a1+t.a2);
                t.epsilon_r=abs(t.b1+t.b2);

                 %Regla de Carter y Criterio de Zweifel
                t.delta_e=0; t.delta_r=0; error_E=1; error_R=1; iteracion_delta=0;
                while((error_E>0.00001 || error_R>0.00001) && iteracion_delta<100)
                    delta_E_prime=t.delta_e;
                    delta_R_prime=t.delta_r;
                    t.a1_prime=t.a1+delta_E_prime;
                    t.b2_prime=t.b2+delta_R_prime;
                    t.calado_e=abs(t.a1_prime-t.a2_prime)/2;
                    t.calado_r=abs(t.b1_prime-t.b2_prime)/2;
                    t.sigma_e=2*(cos(t.a1)^2)*(tan(t.a1)+tan(t.a2))/(0.8*cos(t.calado_e));
                    t.sigma_r=2*(cos(t.b2)^2)*(tan(t.b2)+tan(t.b1))/(0.8*cos(t.calado_r));
                    t.theta_e=t.a2_prime+t.a1_prime;
                    t.theta_r=t.b2_prime+t.b1_prime;
                    t.delta_e=0.19*t.theta_e/t.sigma_e;
                    t.delta_r=0.19*t.theta_r/t.sigma_r;
                    error_E=abs(t.delta_e-delta_E_prime);
                    error_R=abs(t.delta_r-delta_R_prime);
                    iteracion_delta=iteracion_delta+1;
                end
                t.Dm=t.u/(pi*d.n/60);
                T0=d.T0_e-t.c2^2/(2*d.Cp);
                P0=d.p0_e*(T0/d.T0_e)^(d.gamma/(d.gamma-1));
                rho0=P0/(287*T0);
                t.H0=d.m/(pi*t.Dm*t.ca*rho0);
                T1=d.T0_e-t.c1^2/(2*d.Cp);
                %-----------PÉRDIDAS ESTATOR----------------
                zeta_pe=0.025*(1+(t.epsilon_e*2/pi)^2);
                zeta_se=zeta_pe*3.2*t.l_e*cos(t.calado_e)*2/(t.H0+t.H1);
                t.zeta_e=zeta_se+zeta_pe;
                t.Y_e=t.zeta_e*t.c1^2/2;
                %---------------------
                T1s=T1-t.Y_e/d.Cp;
                P1=d.p0_e*(T1s/d.T0_e)^(d.gamma/(d.gamma-1));
                rho1=P1/(287*T1);
                t.H1=d.m/(pi*t.Dm*t.ca*rho1);
                t.l_e=(t.H0+t.H1)/3;
                t.ze=(pi*t.Dm)/(t.l_e/t.sigma_e);
                T2=d.T0_e-t.c2^2/2-d.eta_te*d.T0_e*(1-(d.p_s/d.p0_e)^((d.gamma-1)/d.gamma));
                rho2=d.p_s/(287*T2);
                t.H2=d.m/(pi*t.Dm*t.ca*rho2);
                t.l_r=(t.H2+t.H1)/3;
                t.zr=(pi*t.Dm)/(t.l_r/t.sigma_r);
                %----------PÉRDIDAS ROTOR---------------------
                zeta_pr=0.025*(1+(t.epsilon_r*2/pi)^2);
                zeta_sr=zeta_pr*3.2*t.l_r*cos(t.calado_e)*2/(t.H2+t.H1);
                zeta_ir=0.5*0.5e-3*2/(t.H2+t.H1)*(2*(tan(t.b2)-tan(t.b1))/t.sigma_r)^2*cos(t.b2)^2/cos(t.bm)^3;
                t.zeta_r=zeta_pr+zeta_sr+zeta_ir;
                t.Y_r=t.zeta_r*t.w2^2/2;
                t.Y_4r=0.0095*rho1*(d.n*2*pi/60)^3*t.Dm^5/d.m;

                

               
           

        end
    end
end

Answer 1

[Satwik]

Hi Daniel,

I understand that you have made a class diseno with multiple properties including another class trapecio but when you execute the main class diseno it gives out an error.

This behaviour is happening because in the trapecio constructor

t.u=sqrt(d.wi/PSI); % first line of trapecio constructor

you are trying to access a property wi inside input argument d using dot notation, but inside diseno when you are invoking trapecio in the properties block you are just passing 0 in place of d as an input argument.

trapecio=trapecio(0,0,0,0,0,0) % in the properties block of class diseno

which does not have a 'wi' property to be accessed, that is where the code is throwing an error.

There are many instances in your code where you are accessing some properties of d.

To fix this pass an object in place of d with all the required properties when invoking a trapecio object.

After making the changes make sure to run

clear classes

to update the classes and then execute your code.

Hope this helps!

[Daniel Gonzalo Rodríguez]

Thanks! It already runs!