Sort and keep a unique duplicate which has the highest value

Question

I have a file like the one shown below, I want to keep the combinations between the first and second field which has the highest value on the third field(the ones with the a

Answer 1

Two passes of sort should do it, for example in bash shell

sort -k1,1n -k2,2n -k3,3nr -t$'\t'  file  | sort -k1,1n -k2,2n -t$'\t' -u -s
1       1       12
1       2       6
1       3       4
2       4       40
2       45      15
3       3       19
3       15      9
4       17      36
4       18      4

Answer 2

This is a bit funny, but:

sort -nr myfile.txt | rev | uniq -f1 | rev | sort -n

Output:

1   1   12
1   2   6 
1   3   4 
2   4   40
2   45  15
3   15  9 
3   3   19
4   17  36
4   18  4 

How it works:

• Sort reverse numerically, putting the highest values at the top (so they are saved)
• Reverse each line, so the last field is first (needed for uniq)
• Save only the first uniq line, but ignoring the first field (was the last field)
• Reverse the line back to original order
• Sort the lines from low to high again

Probably not the most efficient in the world, but at least each step makes some sense.