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An error when "syms" is used

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Mahsa Babaee
Mahsa Babaee on 31 May 2021
Closed: Mahsa Babaee on 31 May 2021
Hello
I would be appreciated if you could guide me why the following error has occured in phi(1), phi(2), and phi(3) as symbolic variables?!
Unable to convert expression containing symbolic variables into double array. Apply 'subs' function first to substitute values for variables.
A piece of my code is :
a1 = 5.79e-08; a2 = 1.23e-07; a3 = 6.67e-08; a21=a2/a1; a32=a3/a2;
o1= w1*(Tb-Tts)+q_met1/k1;
o2= w2*(Tb-Tts)+q_met2/k2;
o3= w3*(Tb-Tts)+q_met3/k3;
syms s
syms t
syms x y z
Tb=310; Tts=310; Tini=309; % Assumption: Tb=Tts;
phi= zeros(3,1);
TT= Tini-Tts;
phi(1)= TT+(a1*o1)/s;
phi(2)= TT+(a2*o2)/s;
phi(3)= TT+(a3*o3)/s;
  6 Comments
Mahsa Babaee
Mahsa Babaee on 31 May 2021
I forgot to paste that! o1, o2, o3 and q_met1, q_met2, q_met3 and k1, k2, k3 are all known values!
I just want to define phi as a symbolic array and I did it as Torson explained.
Thank you for your time.

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