MATLAB: Ode 45 question, error message

MATLABode45

I'm having trouble with my ode, it says
"Index exceeds the number of array elements (4)."
global p00
tic
a1 = 500;
a2 = 100;
a3 = 10^16.35
CA0 = 0.005; %FeS2
CB0 = 0.250;  %O2
CC0 = 0;     %Fe2
CD0 = 0.01;  %SO4
CE0 = 0.01; %Fe3
CAt = CA0 + CB0 + CC0 + CD0 + CE0;
CEt = CD0 + CC0 + CB0 + CE0
p00 = [a1;a2;a3];
y0(1) = CA0; % Concentration of initial A - [M]
y0(2) = CB0;
y0(3) = 0;
y0(4)= CD0;
yo(5) = CE0;
dt = 1;
t = (0:dt:60)';
tspan = [0 max(t)];
[T,y] = ode45('RK4odes',tspan,y0);
%


% Mass balance 
%
y(:,4) = CAt-y(:,1)-y(:,2)-y(:,3)-y(:,5)
y(:,5) = CEt-y(:,2)-y(:,3)-y(:,5)
%
toc
% seperate fxn
function RK4odes1= RK4odes(~,y)
global p00
a1 = p00(1);
a2 = p00(2);
a3 = p00(3);
RK4odes1(1,1) = -a1*(y(1)^0)*y(5)*(y(4)^-1)*10^-7 - a2*y(2)*(y(1)^0)*(y(4)^-1)*10^-7; % CA
RK4odes1(2,1) = -a2*(y(1)^0)*(y(3)^0)*(y(4)^-1)*10^-7 - a3*(y(3)^0)*y(2)*10^-7 % CB O
RK4odes1(3,1) = a2*(y(1)^0)*y(2)*(y(4)^-1)*10^-7 -a3*y(2)*(y(3)^0)*(y(4)^-1); % CC Fe2
RK4odes1(4,1) = a1*(y(1)^0)*y(5)*(y(4)^-1)*10^-7 +a2*y(2)*(y(1)^0)*(y(4)^-1)*10^-7;
RK4odes1(5,1) = -a1*(y(1)^0)*y(5)*(y(4)^-1)*10^-7 +a3*y(2)*(y(3)^0)*(y(4)^-1) 
end

Best Answer

This: 
yo(5) = CE0;
should probably be: 
y0(5) = CE0;
It likely does not help that ‘o’ and ‘0’ are next to each other on most keyboards!
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