Problem with a fuction

In my opinion your program is far too large and clutterd and should be split into parts.

The error is thrown at this line

because A is not a vector but a 3 x 3 matrix (and would require tw indices zo access elements).

The argument vector A is overwritten by your program here

and is a 3 x 3 matrix because you made the variable a a 3 x 3 matrix here:

Regards Werner

There are many products poorly written. That is, to make the product, you have not used the product operator. The program is full of such errors.

The dot corresponding to the product is sometimes seen and sometimes not. It seems to me a mistake.

Bye

zbs:

The Value A must be a vector, but in the program A is calculated from matrix a.