Why am I getting an : Error using sym/subsasgn (line 1058) Invalid indexing or function definition. Indexing must follow MATLAB indexing. Function arguments must be symbolic

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Hazel Can 2022-4-5

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回答： R 2024-1-25

Hello, I am writing a code to solve my Forward Euler Method question. I added my question here.

I am encountering an error while writing the code; error :

Error using sym/subsasgn (line 1058)

Invalid indexing or function definition. Indexing must follow MATLAB indexing. Function arguments must be symbolic variables, and function body must be sym expression.

I would be very grateful if you could help me how to fix this error.

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Torsten 2022-4-5

You did not include the part of your code where you use symbolic variables now conflicting with a numerical computation.

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Answer 1

R 2024-1-25

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Hello Hazel,

This error occurs when using a symbolic variable as both a summation index for the "symsum" function and an index into an array. The "symsum" function requires the summation index to be a symbolic variable type, but as far as I understand, MATLAB indexing rules do not currently allow indexing into an array with a symbolic variable.

To work around this, compute the series with a for-loop instead.

I hope this addresses the error you are facing.