Subscript indices must either be real positive integers or logicals.

I was trying to use the Newton–Raphson method to do it but I keep getting this error code ''Subscript indices must either be real positive integers or logicals.''

I have attached the data provided to me and the flowchart I was following to get this program.

clc
close all  
clear 

% Data provided 
load('SD_Test_Data_01.mat', 'voltage')
load('SD_Test_Data_01.mat', 'current')
I = current;
V = voltage;
P = I.*V; % To find the P-V curve 
Pmaxcurve = max(P);

% Graphs
figure(1);
plot (V, I,'b:')
xlabel('Voltage (V)'), ylabel('Current (A)')
title('I-V Curve')

figure(2);
plot(V, P,'r--');
xlabel('Voltage(V)'), ylabel('Power (W)')
title('P-V Curve')

figure(3);
plot (V, I,'--')
title('Combine Plots')
hold on
plot(V, P, 'r:'); 
hold off

%At the standard test conditions (STC)
[Pmax, index_of_Pmax] = max(P);
Imp = I(index_of_Pmax); %(A) 
Vmp = V(index_of_Pmax); %(v)

%We know that
Isc = max(I); %(A)
Voc = max(V); %(V)
q = 1.6022e-19; %q is the electron charge
k = 1.3806e-23; % k is the Boltzmann constant in (J/k)
% if the solar cells inside a solar module reach 65?C
T = 25; % T the module temperature in celcius
 
% Initializing Rs the series resistance and the shunt resistance Rsh and n
Rsh = (Vmp/(Isc- Imp))- ((Voc-Vmp)/Imp);
Rs = 0;
n= 1.2;

% Taking an assumption that Rsh>>Vo
I0 = Isc/(exp(1)*(q(Voc/(n*k*T)))-1);

Nmax = 100; %maximum number of interations
g(1) = 0.5; %first approximation

for a = zeros(1, Nmax-1)
    g(a+1) = g(a) - (Isc-I0(exp(q((Vmp+Imp*Rs)/n))-1) - ((Vmp+(Imp*Rs))/n*k*T)) / (-I0((q/(nkT))*(1+diff(I, V)*Rs)*exp(1)*(q(V+(I*Rs)/(nkT)))))-(1/Rsh)*(1 + diff(I, V)*Rs);
end
plot(g, 'r.')

Answer 1

[James Tursa]

This line produces indexes of zeros:

for a = zeros(1, Nmax-1)

I think you meant this instead:

g = zeros(1, Nmax);
for a = 1:Nmax-1

Also, I would assume everywhere you have I0( you meant I0*(

Same comment for q( probably meant q*(

[Joanan Destin]

I followed your advice and now I got this error

% %

Error using diff

Difference order N must be a positive integer scalar.

Error in Esram (line 56)

g(a+1) = g(a) - (Isc-I0*(exp(1)*(q*((Vmp+(Imp*Rs))/n))-1) - ((Vmp+(Imp*Rs))/(n*k*T))) / (-I0*((q/(n*k*T))*(1 + diff(I, V)*Rs)*exp(1)*(q*(V+(I*Rs)/(n*k*T)))))-(1/Rsh)*(1 + diff(I, V)*Rs);

here is the updated program

clc
close all  
clear 

% Data provided 
load('SD_Test_Data_01.mat', 'voltage')
load('SD_Test_Data_01.mat', 'current')
I = current;
V = voltage;
P = I.*V; % To find the P-V curve 
Pmaxcurve = max(P);

% Graphs
figure(1);
plot (V, I,'b:')
xlabel('Voltage (V)'), ylabel('Current (A)')
title('I-V Curve')

figure(2);
plot(V, P,'r--');
xlabel('Voltage(V)'), ylabel('Power (W)')
title('P-V Curve')

figure(3);
plot (V, I,'--')
title('Combine Plots')
hold on
plot(V, P, 'r:'); 
hold off

%At the standard test conditions (STC)
[Pmax, index_of_Pmax] = max(P);
Imp = I(index_of_Pmax); %(A) 
Vmp = V(index_of_Pmax); %(v)

%We know that
Isc = max(I); %(A)
Voc = max(V); %(V)
q = 1.6022e-19; %q is the electron charge
k = 1.3806e-23; % k is the Boltzmann constant in (J/k)
% if the solar cells inside a solar module reach 65?C
T = 25; % T the module temperature in celcius
 
% Initializing Rs the series resistance and the shunt resistance Rsh and n
Rsh = (Vmp/(Isc- Imp))- ((Voc-Vmp)/Imp);
Rs = 0;
n= 1.2;

% Taking an assumption that Rsh>>Vo
I0 = Isc/(exp(1)*(q*(Voc/(n*k*T)))-1);

Nmax = 1000; %maximum number of interations
g(1) = 0.5; %first approximation
g = zeros(1, Nmax);
for a = 1:Nmax-1
    g(a+1) = g(a) - (Isc-I0*(exp(1)*(q*((Vmp+(Imp*Rs))/n))-1) - ((Vmp+(Imp*Rs))/(n*k*T))) / (-I0*((q/(n*k*T))*(1 + diff(I, V)*Rs)*exp(1)*(q*(V+(I*Rs)/(n*k*T)))))-(1/Rsh)*(1 + diff(I, V)*Rs);
end
plot(g, 'r.')