I have used the following formula for two columns of data:
{=average(if(B1:B50="",A1:A50,"NA"))}
This works well for me to calculate the average of A1:A50 where I put a * in
the B column to exclude some data. I do the same thing for the median
calculation as well.

My question is: Is there a way to use this same type of format to calculate
the average if I am filtering a column so that some rows are excluded?

I have tried: {=subtotal(109,if(B1:B50="",A1:A50,"NA"))} and it does not
seem to work. Any suggestions appreciated.