Average of multiple files without considering missing values

Question

I want to calculate the average of 15 files:- ifile1.txt, ifile2.txt, ....., ifile15.txt. Number of columns and rows of each file are same. But some of them are missing values.

Answer 1

awk '
   {
   for (i = 1;i <= NF;i++) {
      Sum[FNR,i]+=$i
      Count[FNR,i]+=$i!="?"
      }
   }
END {
   for( i = 1; i <= FNR; i++){
      for( j = 1; j <= NF; j++) printf "%s ", Count[i,j] != 0 ? Sum[i,j]/Count[i,j] : "?"
      print ""
      }
   }
' ifile*

assuming file are correctly feeded (no trailing empty space line, ...)