Empty Sym when using vpasolve-operator.

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Iver Brekken
Iver Brekken 2022-1-20
编辑： Torsten 2022-1-20
e = [0.05:0.05:1];
syms tp
eqn = 900-e.*5.67*10^(-8)*tp^4-20*(tp-293)==0;
S = vpasolve(eqn,tp)
I get the following message: Empty Sym: 0-by-1 when running this. Any changes I can make?

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回答（1 个）

Torsten
Torsten 2022-1-20
e = [0.05:0.05:1];
syms tp
for i=1:numel(e)
eqn = 900-e(i)*5.67*10^(-8)*tp^4-20*(tp-293)==0;
S{i} = vpasolve(eqn,tp);
end
  2 个评论
Iver Brekken
Iver Brekken 2022-1-20
Thank you! I want to plot S vs e (e at x-axis), and use the second element of every cell in S to do so. Any help?
Torsten
Torsten 2022-1-20
编辑：Torsten 2022-1-20
e = [0.05:0.05:1];
syms tp
for i=1:numel(e)
eqn = 900-e(i)*5.67*10^(-8)*tp^4-20*(tp-293)==0;
S(i) = double(vpasolve(eqn,tp));
end
plot(e,S)
end
Maybe you should use "roots" instead of "vpasolve" because your polynomial equation has 4 zeros.

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