Does passing a dataframe declared outside a function as an argument improves performance?

[bkamins]

@DNF

Whether it impacts performance in your particular case is hard to say without more detail, but passing it as an argument is either as fast or faster, and possibly much faster.

DataFrame is type unstable, so the performance should not be affected as I have commented above.
(passing it to a function might give time improvement of nanosecond order as it will avoid dynamic dispatch in the function scope, but it will not be noticeable in practice)

However, what @DNF comments it indeed a valid general recommendation in Julia and should be followed.