which sym class(sym) Gup=sym(zeros(2,2))
I put "which sym" before the sym statement and I still get this error"
??? Subscript indices must either be real positive integers or logicals.
Error in ==> CoAndContraMetricTensors at 7 Gup=sym(zeros(2,2))
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Gup = sym(zeros(2,2));
works. Therefore the error must be coming from somewhere else in your CoAndContraMetricTensors.m file. You do know that sym() is a MATLAB function so are you also using it as a variable in the M-file?
You don't show us what which sym returns.
In your other Question, when I said to put in
which sym class(sym)
it was a request for you to show us (the people trying to assist you) what those two lines output. The two lines are not intended to repair anything, they are intended to give us volunteers information to better understand your problem. You need to show us the output of those two lines.