How do I store values from a while loop and plot the values in fonction of the number of iteration?

Hello!

In the loop while I would like to store the values of each loop, and plot it with the corresponding iteration t.

m_cafe=0.2; %kg
m_cream=0.05; %kg
Cp_water=4179,6;
T_cafe=5+273.15; %K
T_cream=90+273.15;
m_mix=m_cafe+m_cream;
Tm=(m_cafe*Cp_water*T_cafe+m_cream*Cp_water*T_cream)/(m_mix);
U=20; %W/m2.K
Tamb=20+273.15; %K
d=0.05; %m
r=d/2; %m
Vol_cafe=m_cafe*0.001 % 1 kg=1 liter= 0.001m3
Vol_mix=m_mix*0.001 %
h_cafe=Vol_cafe/(3.14*r^2)
h_mix=Vol_mix/(3.14*r^2)
Air_cafe=3.14*d*h_cafe
Air_mix=3.14*d*h_mix
step=0.5;
e=1
t=0
while e>=0.01

y=(Tm-Tamb)*exp(((-Air_mix*U)/(m_mix*Cp_water))*t)+Tamb;
Temp(t)=y;
e=abs(Temp-Tamb);
t=t+step

end
plot (t,Temp,'r')

[Rik]

This time I edited your question for you. Next time, please use the tools explained on this page to make your question more readable.

Answer 1

[Rik]

Indices in Matlab need to be positive integers. You should create a separate time vector.

And don't forget to index Temp, otherwise your condition will be a vector.

[Rik]

Comment posted as answer by Sarah Mignon:

e=1
t=1
while e>=0.01

y=(Tm-Tamb)*exp(((-Air_mix*U)/(m_mix*Cp_water))*t)+Tamb;
Temp(t)=y;
e=abs(Temp(t)-Tamb);
t=t+step
Time(t)=t

end
plot (t,Temp,'r')

Thank you for your answer. Is it what you meant? I have tried to set t=1 to have a positive integers but it still gives me the same errror "Array indices must be positive integers or logical values." Is it the right way to store values in a vector?Is there a way to use "Append" in matlab? Also How can I have a graph starting from t=0 then with the corresponding values of Temp?

[Rik]

You need to use a separate index, which will increment only by integer values:

t=0;
Temp=0;
n=1;
e=1;
while e>=0.01
    n=n+1;
    Temp(n)=___
    t(n)=t(n-1)+step;
end
plot(t,Temp)

[Sarah Mignon]

Thank you for your help, I made it working