calculating average using awk from multiple files

Question

I have 500 files with name fort.1, fort.2 ... fort.500. Each file contains 800 data as below:

1 0.485
2 0.028
3 0.100

Answer 1

Assuming the first column is an ID:

cat fort.* | awk '{sum[$1] += $2; counts[$1]++;} END {for (i in sum) print i, sum[i]/counts[i];}'