Index exceeds the number of array elements (1).

Hi community Matlab, My programme is generating the following error,

if true
  function dxdt = semibrx(t,x,k,Kc,V0,v0,Cb0)
% x(1)= Ca, x(2) = Cb, x(3) = Cc, x(4) = Cd;
rA = -k*(x(1)*x(2)-(1/Kc)*x(3)*x(4));
V = V0+v0*t;
dxdt = [
  rA-(v0/V)*x(1);
  rA + (v0/V)*(Cb0-x(2));
 -rA-(v0/V)*x(3);
 -rA-(v0/V)*x(4)
 ]
end 

if true
  clear all;
k = 9e-5; v0= 0.05 ; V0 = 200; Cb0 = 10.93; Ca0= 7.72;
Kc = 1.08;
x0 = [Ca0 0 0 0 ]; tspan = [0 1e2];
[t x] = ode45(@equilibrio,tspan,Kc,x0,[],k,v0,V0,Cb0);
Ca = x(:,1);
Cb = x(:,2);
Cc = x(:,3);
Cd = x(:,4) ;
V = V0 + v0*t; Xa = (Ca0*V0-Ca.*V)/(Ca0*V0); rA = -k*(x(1)*x(2)-(1/Kc)*(x(3)*x(4)));
%subplot(1,2),
plot(t,Ca,t,Cb,':',t,Cc,'.-',t,Cd,'--');
xlabel('t(s)'),ylabel('Concentration(mol/dm^3)'), legend ('C_A','C_B','C_C','C_D')
%subplot(1,2),
%plot(t,rA), xlabel('t(s)'),ylabel ('Reaction rate (mol/dm^3s)')
%plot(t,Xa),xlabel('t(s)'),ylabel('Conversão')
end
end

The program shows error: Index exceeds the number of array elements(1).

Would you help me please?

Thanks,

Guilherme Lopes de Campos

[Guillaume]

When you report an error always give us the full text of the error message, everything in red. In particular, we're missing the line that causes the error.

In any case, the error message is clear, you're trying to index something that has only one element with an index greater than 1. Check the size of that something and make sure that it's big enough for what you want. I suspect the something is x.

[TADA]

If you remove the

if true

and put function declerations in the end of the script, your code will be more readable.

what line of code does your error come from?

[Guilherme Lopes de Campos]

if true

Index exceeds the number of array elements (1).

Error in equilibrio (line 3) rA = -k*(x(1)*x(2)-(1/Kc)*x(3)*x(4));

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

Error in ode45 (line 115) odearguments(FcnHandlesUsed, solver_name, ode, tspan, y0, options, varargin);

Error in equilibrio2 (line 5) [t x] = ode45(@equilibrio,tspan,Kc,x0,[],k,v0,V0,Cb0);

end

[madhan ravi]

See my answer below

[Guilherme Lopes de Campos]

Thank you very much Community, for help!

Answer 1

[madhan ravi]

clear all;
Ca0= 7.72;

x0 = [Ca0 0 0 0 ]; tspan = [0 1e2];
[t x] = ode45(@equilibrio,tspan,x0);   %FUNCTION CALLING
Ca = x(:,1);
Cb = x(:,2);
Cc = x(:,3);
Cd = x(:,4) ;
figure
plot(t,Ca)
xlabel('t(s)')
ylabel('Concentration(mol/dm^3)')
legend ('C_A')
figure
plot(t,Cb,':')
xlabel('t(s)')
ylabel('Concentration(mol/dm^3)')
legend('C_B')
figure
plot(t,Cc,'.-')
xlabel('t(s)')
ylabel('Concentration(mol/dm^3)')
legend ('C_C')
figure
plot(t,Cd,'--')
xlabel('t(s)')
ylabel('Concentration(mol/dm^3)')
legend ('C_D')

function dxdt = equilibrio(t,x)
k = 9e-5; v0= 0.05 ; V0 = 200; Cb0 = 10.93; 
Kc = 1.08;rA = -k*(x(1)*x(2)-(1/Kc)*x(3)*x(4));
V = V0+v0*t;
dxdt = [rA-(v0/V)*x(1);
  rA + (v0/V)*(Cb0-x(2));
 -rA-(v0/V)*x(3);
 -rA-(v0/V)*x(4)]
end

[Guilherme Lopes de Campos]

Thank you very much Madhan!

[madhan ravi]

Anytime :)