Why am I getting the error "Too many output arguments"?

%initialise paramteres 
A = 1.7;               
k = 1.380658*(10^-23);  
q = 1.6 * (10^-19);     
Eg = 1.1;               
Ior = 19.9693*(10^-6);  
Iscr = 3.3;              
ki = 1.7 * (10^-3);     
ns = 40;                
np = 2;                 
Rs = 5*(10^-5);         
Rp = 5*(10^5);         
Tr = 301.18;            

Ta = 25;                

%array error = 1;
amb = [25 40 60];
irr = [0.3 0.5 1]; 

%Evaluate 


hold on 

for i=1:3
    Ipv = [];
    Vpv = [];
    Ppv = [];
    
    G= irr(i);                  
    Tc = Ta + (0.2*G) + 273.18;                           
    Isc = (Iscr + ki*(Tc-Tr))*G;            
    Is = Ior * ((Tc/Tr)^3) * exp(q*Eg*(1/Tr-1/Tc)/(k*A)); 
    I = Isc;                                       
    V = 0;                                     
    
    while I>0 
        while error>0.0001
            f1= I-(np*Isc)+(np*Is)*(exp(q*((V/ns)+(I*Rs/np))/(A*k*Tc))-1)+(((V*np/ns)+(I*Rs))/(Rp));
            df1= 1+(Rs/Rp)+((q*Is*Rs)/(A*k*Tc))*(exp(q*((V/ns)+(I*Rs/np))/(A*k*Tc)));
            I= I-(f1/df1);
            error=abs(f1/df1);
        end
        
        Ipv= [Ipv I];
        Vpv = [Vpv V];
        Ppv= [Ppv I*V];
        V = V+0.1;
        error = 1; 
    end 
    
    
    plot(Vpv, Ipv);
    
    
    % plot(Vpv, Ppv);
    
end 

Error using error
Too many output arguments.

Answer 1

[the cyclist]

You are confusing MATLAB by using error (a MATLAB function) as a variable name.

I changed that variable name to errorVal, and initialized it to -Inf.

%initialise paramteres 
A = 1.7;               
k = 1.380658*(10^-23);  
q = 1.6 * (10^-19);     
Eg = 1.1;               
Ior = 19.9693*(10^-6);  
Iscr = 3.3;              
ki = 1.7 * (10^-3);     
ns = 40;                
np = 2;                 
Rs = 5*(10^-5);         
Rp = 5*(10^5);         
Tr = 301.18;            

Ta = 25;                

%array error = 1;
amb = [25 40 60];
irr = [0.3 0.5 1]; 

%Evaluate 

errorVal = -Inf;

hold on 
for i=1:3
    Ipv = [];
    Vpv = [];
    Ppv = [];
    
    G= irr(i);                  
    Tc = Ta + (0.2*G) + 273.18;                           
    Isc = (Iscr + ki*(Tc-Tr))*G;            
    Is = Ior * ((Tc/Tr)^3) * exp(q*Eg*(1/Tr-1/Tc)/(k*A)); 
    I = Isc;                                       
    V = 0;                                     
    
    while I>0 
        while errorVal>0.0001
            f1= I-(np*Isc)+(np*Is)*(exp(q*((V/ns)+(I*Rs/np))/(A*k*Tc))-1)+(((V*np/ns)+(I*Rs))/(Rp));
            df1= 1+(Rs/Rp)+((q*Is*Rs)/(A*k*Tc))*(exp(q*((V/ns)+(I*Rs/np))/(A*k*Tc)));
            I= I-(f1/df1);
            errorVal=abs(f1/df1);
        end
        
        Ipv= [Ipv I];
        Vpv = [Vpv V];
        Ppv= [Ppv I*V];
        V = V+0.1;
        errorVal = 1; 
    end 
    
    
    plot(Vpv, Ipv);
    
    
    % plot(Vpv, Ppv);
    
end

Answer 2

[Torsten]

You don't initialize "error" in your code by giving it a value before you use it in the while loop.

That's why MATLAB assumes error to be the built-in "error" command:

https://uk.mathworks.com/help/matlab/ref/error.html

Answer 3

[Walter Roberson]

You do not initialize error before you use it.

error happens to be the name of an important Mathworks function -- a function that is not permitted to return a value and so cannot exist in a form

while error>0.0001

Best would be if you used a different variable name (and made sure to initialize it). Compromise would be if you assigned to error before you use it.