How can I plot values of a for loop?

Hey guys, when I run this code I get an output with every value for Tc and Q. But these values won't plot, I just get a blank plot with no dots or lines. I have tried using both plot and plotyy, none of them work. Please help me.

%Given values:

d=0.35; % (m)

k=14.9; % (W/m.K)

r=d/2;

ro=7900; % (kg/m^3)

cp=0.477; % (kJ/kg.K)

a=3.95*10^-6; % (m^2/s)

Ti=400+273; % (K)

h=60; % (W/m^2.K)

Ts=150+273; % (K)

%Finding biot number:

Bi=(h*r/k);

%Values obtained from table:

l=1.0935; %lambda

A=1.1558;

J=0.4689;

%Finding Qmax:

m=ro*pi*r^2*1;

Qmax=m*cp*(Ti-Ts);

Tc=0;

Q=0;

%Generating temperature and heat transfer numbers

for t=5*60:60:60*60

tau=((t*a)/r^2);

Tc=(Ts+((Ti-Ts)*(A*exp(l^2*(-tau)))))

Q=(Qmax*(1-(2*((Tc-Ts)/(Ti-Ts))*(J/l))))

end

t=[5*60:60:60*60];

%ploting values

[hAx,hLine1,hLine2] = plotyy(t,Tc,t,Q)

xlabel('Time (s)')

ylabel(hAx(1),'Center temperature (K)')

ylabel(hAx(2),'Heat transfer (kJ)')

title('Center temperature and heat transfer as a function of time')

Answer 1

[Roger Stafford]

In your for loop you are not placing the successive values of Tc and Q in vectors. Instead they are being overwritten so that only the last pair is available for plotting. Change to:

   t=5*60:60:60*60;
   for k = 1:length(t);
     tau = ...
     Tc(k) = ...
     Q(k) = ...
     etc.

[Patricia]

I changed it to this:

 t=[5*60:60:60*60];
for k=1:length(t)
tau(k)=((t*a)/r^2);
Tc(k)=(Ts+((Ti-Ts)*(A*exp(l^2*(-tau)))))
Q(k)=(Qmax*(1-(2*((Tc-Ts)/(Ti-Ts))*(J/l))))
end

but now it gives me this error:

In an assignment A(I) = B, the number of elements in B and I must be the same.

Error in HT461 (line 28) tau(k)=((t*a)/r^2);

[Patricia]

I figured it out! thanks.

Answer 2

[Patricia]

I changed it to this:

 t=[5*60:60:60*60];
for k=1:length(t)
tau(k)=((t*a)/r^2);
Tc(k)=(Ts+((Ti-Ts)*(A*exp(l^2*(-tau)))))
Q(k)=(Qmax*(1-(2*((Tc-Ts)/(Ti-Ts))*(J/l))))
end
but now it gives me this error:

In an assignment A(I) = B, the number of elements in B and I must be the same.

Error in HT461 (line 28) tau(k)=((t*a)/r^2);

[Star Strider]

See if subscripting ‘t’ as ‘t(k)’ corrects that.