About expm function error

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)

[ZHICHEN LIU]

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)

Answer 1

[Walter Roberson]

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

[ZHICHEN LIU]

I checked my variable in my workspace, there is no leftover varibale named expm.

[ZHICHEN LIU]

Is there possible M1 chip not compatible to 2019b version?

[Walter Roberson]

R2019b was not supported on the M1.

[ZHICHEN LIU]

Thank you, I think that could be the reason why it gave me an error.

[ZHICHEN LIU]

Solved the issue by resigned in my account...

Answer 2

[William Rose]

@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.

[ZHICHEN LIU]

Is there possible M1 chip not compatible to 2019b version?

[William Rose]

@ZHICHEN LIU,

The code you posted ran fine, without error, in 2018b and 2021a versions. I don;t have 2019.

[ZHICHEN LIU]

thank you so much, I solved issue by resign in my account.