Error using sym/subindex

Question

Daniel Murphy 2022-2-26

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1659110-error-using-sym-subindex

回答： Walter Roberson 2022-2-26

Good morning,

I've been transcribing code from a course to modify for my homework, however I run into the error, "Error using sym/subindex (line 953) when it goes to calculate a(j) when using Matlab Online. However, as shown below it runs when inputted into the forums version of Matlab.

Screenshot of Error:

My Code:

syms t p po T0 j

w0 = 2*pi/T0

p(t) = (po/T0)*t

a0 = 1/T0*int(p(t),t,0,T0)

a(j) = 2/T0*int(p(t)*cos(j*w0*t),t,0,T0)

syms t p po T0 j

w0 = 2*pi/T0;

p(t) = (po/T0)*t;

a0 = 1/T0*int(p(t),t,0,T0);

a(j) = 2/T0*int(p(t)*cos(j*w0*t),t,0,T0)

a(j) =

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Walter Roberson 2022-2-26

Works for me in MATLAB Online

Daniel Murphy 2022-2-26

Restarted my computer and disconnected the previous session. That fixed it. I assume it's some sort of bug with connectivity to the server. Thanks.

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Answer 1

Daniel Murphy 2022-2-26

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https://ww2.mathworks.cn/matlabcentral/answers/1659110-error-using-sym-subindex#answer_905175

Appears to have been a bug with connection to the server. Was fixed by trestarting computer and disconnecting from the previous Matlab session.

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Answer 2

Walter Roberson 2022-2-26

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https://ww2.mathworks.cn/matlabcentral/answers/1659110-error-using-sym-subindex#answer_905185

What you describe could happen in two ways:

if a already exists in the workspace somehow
if you were using r2019b or earlier, then if I recall correctly, the names pi, i, j, psi, and euler had special meaning as symbols and could not be used as variable names for defining the parameters of a symbolic function.