convert array formula output to string

Hi all,

I'm trying to turn the output of an array formula to a string so that i can use it inside an INDIRECT formula. My array formula is the following:

=IF(R3:R14=1,Q3:Q14&ROW(),"")

Column Q has letters in it (C through N) and R is 1 or 0 for each letter. In the end, I want the string to look something like this:

"C2,D2,E2,F2..." (assuming the formula was entered in cell O2)

Using this string, I would then be able to write an AVERAGE around it:

=AVERAGE(INDIRECT(---string---))

Thanks,
Joe