Kayan Kayan - 6 months ago 5
Linux Question

Print a selective column after subtraction from another file

I have two files with equal number of rows and columns. I would like to subtract the 2nd column in one file from the 2nd column in another file without considering the missing values. e.g.

ifile1.txt
3 5 2 2
1 ? 2 1
4 6 5 2
5 5 7 1

ifile2.txt
1 2 1 3
1 3 0 2
2 ? 5 1
0 0 1 1


Here "?" is the missing value and should not be considered in computation.

ofile.txt i.e. [$2(ifile1.txt) - $2(ifile2.txt)]
3
?
?
5


I could able to do it without any missing values in following way. But can't able to succeed with a missing value like here "?".

paste ifile1.txt ifile2.txt > ifile3.txt
awk '{n=NF/2; for (i=1;i<=n;i++) printf "%5.2f ", $i-$(i+n); print ""}' ifile3.txt > ifile4.txt
awk '{printf ("%.2f\n",$2)}' ifile4.txt > ofile.txt

Answer
$ awk 'NR==FNR{a[NR]=$2;next} {print ((a[FNR]$2)~/?/ ? "?" : a[FNR]-$2)}' file1 file2
3
?
?
5
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