About expm function error

2022 2 3
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更新时间：2022 2 3
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Can someone help me?
I am trying to use expm function in matlab to do some calculation. However, everytime I use the expm() function, the system give me an error.
I want to use expm(M) not exp(M).
syms a b x;
H=[a*b,x;a,x-b];
M=int(H,x);
M
expm(M)

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ZHICHEN LIU
ZHICHEN LIU 2022-2-3
the error code from the matlab(I don't know how to fix it, please help me!)
Error using sym/subsindex (line 864)
Invalid indexing or function definition. Indexing must follow MATLAB indexing. Function arguments must be
symbolic variables, and function body must be sym expression.
Error in sym/subsref (line 909)
R_tilde = builtin('subsref',L_tilde,Idx);
Error in untitled (line 5)
expm(M)

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 采纳的回答

Walter Roberson
Walter Roberson 2022-2-3

1 个投票

You have a leftover variable in your workspace that is named expm so MATLAB thinks that you are indexing.

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ZHICHEN LIU
ZHICHEN LIU 2022-2-3
I checked my variable in my workspace, there is no leftover varibale named expm.
ZHICHEN LIU
ZHICHEN LIU 2022-2-3
Is there possible M1 chip not compatible to 2019b version?
Walter Roberson
Walter Roberson 2022-2-3
R2019b was not supported on the M1.
ZHICHEN LIU
ZHICHEN LIU 2022-2-3
Thank you, I think that could be the reason why it gave me an error.
ZHICHEN LIU
ZHICHEN LIU 2022-2-3
Solved the issue by resigned in my account...

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更多回答（1 个）

William Rose
William Rose 2022-2-3
Ran in:

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Ran in:
@ZHICHEN LIU,
I do not get an error when I run the code.
syms a b x;
H=[a*b,x;a,x-b];
M=int(H,x);
M
M = 
expm(M)
ans = 
See above.

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ZHICHEN LIU
ZHICHEN LIU 2022-2-3
Is there possible M1 chip not compatible to 2019b version?
William Rose
William Rose 2022-2-3
@ZHICHEN LIU,
The code you posted ran fine, without error, in 2018b and 2021a versions. I don;t have 2019.
ZHICHEN LIU
ZHICHEN LIU 2022-2-3
thank you so much, I solved issue by resign in my account.

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