How to fix "index exceeds number of arrays error (1)" on my code

Below is my function script:

function dcdt = func3a1(t,c)
global n aEG aCBH aBG Km1 Km2 Km3 Kg1 Kg2 Kg3 Kc1 Kc2 c0

%summations
A = 0;
for j = 3:n
    A = A + c(j);
end 

B = 0;
for k=3:n
    B = B +(k-1)*c(k);
end

a = aEG./(B+Km1.*(1+c(1)./Kg1 + c(2)./Kc1));
b = aCBH./(A+Km2.*(1+c(1)./Kg2 + c(2)./Kc2));
r = aBG./(c(2)+Km3.*(1+c(1)./Kg3));

%differential equations of c1 and c2
dcdt(2)= 2*a*A + b*(A+c(4)) - r*c(2); 
dcdt(1)= 2*a*A + b*c(3) + 2*r*c(2);

%differential equations for c(n=3:98)
for i = 3:n-2
    dcdt(i,1) = a*2*(A-(i-1)*c(i))+b*(c(i+2)-c(i));
end 

%differential equation for n=100 and n=99
dcdt(n) = a*(n-1)*c(n)-b*c(n);
dcdt(n-1) = a*(2*A-(n-2)*c(n-1));

end

And this is my ode solver script:

global n aEG aCBH aBG Km1 Km2 Km3 Kg1 Kg2 Kg3 Kc1 Kc2 c0

% Initial conditions and setup
n = 100;
c0 = 0.6; %mmol/L
aEG = 7; %mmol/L/h
aCBH = 12; %mmol/L/h
aBG = 6; %mmol/L/h
Km1 = 10; %mmol/L
Km2 = 1; %mmol/L
Km3 = 1; %mmol/L
Kg1 = 1; %mmol/L
Kg2 = 1; %mmol/L
Kg3 = 1; %mmol/L
Kc1 = 20; %mmol/L
Kc2 = 20; %mmol/L
x = (0:0.1:5);  % the range of x
z = zeros(size(x));  % allocate the result y
y(1) = c0;  % the initial y value

% The loop to solve the DE
[t,c] = ode15s(@func3a1,x,y); 

%plots
figure(1)
plot(t,y(:,1),t,y(:,2));
xlabel('Time (h)');
ylabel('Concentrations');
legend('c1','c2');

I keep getting this error when I run my function and ode scripts:

Index exceeds the number of array elements (1).

Error in func3a1 (line 9)
    A = A + c(j);

Error in odearguments (line 90)
f0 = feval(ode,t0,y0,args{:});   % ODE15I sets args{1} to yp0.

Error in ode15s (line 150)
    odearguments(FcnHandlesUsed, solver_name, ode, tspan, y0, options, varargin);

Error in Ex1_3a (line 25)
[t,c] = ode15s(@func3a1,x,y);

Why does this keep appearing and how can I fix it?

Answer 1

[Kevin Chng]

Your error is from

for k=3:n
    B = B +(k-1)*c(k);
end

In your main script, n = 100, means that you are going to indexing c(3),c(4),..., until c(100).

The size of c is inherit from y in the main script, y has one size which is y(1) = c0.

Therefore, when accessing c(3), the index is exceed the dimenson of c.