linux - Average of multiple files with unequal row sizes in Shell -

i have 15 datafiles unequal row sizes, number of columns in each file same. e.g.

ifile1.dat   ifile2.dat  ifile3.dat , on ............   0   0        0   0       1   6           1   2        5   3       2   7   2   5        6   10      4   6   5   2        8   9       5   9   10  2        10  3       8   2 

in each file 1st column represents index number. compute average of these files each index number in column 1. i.e.

ofile.txt  0   0     [this computed (0+0)/2]  1   4     [this computed (2+6)/2]  2   6     [this computed (5+7)/2]  3         [no value]  4   6     [this computed (6)/1]  5   4.66  [this computed (2+3+9)/3]  6   10  7     8   5.5  9     10  2.5 

i can't think of simple method it. thinking of method, seems lengthy. taking average after converting files same row size, .e.g.

ifile1.dat   ifile2.dat  ifile3.dat , on ............    0   0        0   0       0   0             1   2        1           1   6     2   5        2           2   7     3            3           3    4            4           4   6   5   2        5   3       5   9   6            6   10      6   7            7           7   8            8   9       8   2   9            9           9   10  2        10  3       10 

$ awk '{s[$1]+=$2; c[$1]++;} end{for (i in s) print i,s[i]/c[i];}' ifile*.dat 0 0 1 4 2 6 4 6 5 4.66667 6 10 8 5.5 10 2.5 

in above code, there 2 arrays, s , c. s[i] sum of entries index i , c[i] number of entries index i. after have read files, print average, s[i]/c[i], each index i.