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Multiplication of a column from 2 files using awk

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# 1  
Old 08-13-2013
Multiplication of a column from 2 files using awk
Hi,

I have two files (file1.txt, file2.txt) in which, I would like to multiply all the values in file1 with the first row value of file2, file1 * second row value of file2, file1 * third row value of file2 and so on.

Below are my sample data.
Code:
file1.txt   file2.txt                  desired outputs   
2              2          out1.txt (file1.txt*2)   out2.txt(file1.txt*3)     
3              3                 4                     6 
4              4                 6                     9    
6                                8                     12
8                                12                    18 
                                 16                    24
 and so on

Thank you very much for any help.
# 2  
Old 08-13-2013
What have you tried?
# 3  
Old 08-13-2013
Hi,

I tried something like this but it doesnt even get past the first line. Smilie

Code:
for i in {1..3}
      do awk 'NR==$i{print $1}' file2.txt > $i.tmp
           paste file1.txt  $i.tmp | awk '{print $1*$2}' > "out$i.txt"
done

Thanks.
# 4  
Old 08-14-2013
The for i in {1..3} works in some shells, but not others. Since the first line of your script doesn't specify what shell you want, it will run using your system's default shell. Then $i in your awk command will not be an expansion of your shell variable; it will reference $0 (the entire input line) since the variable i in your awk script is undefined.
You could try something like:
Code:
awk '
FNR == NR {
        f1[++fc1] = $1
        next
}
{       fn = sprintf("out%d.txt", FNR)
        for(i = 1; i <= fc1; i++) printf("%d\n", $1 * f1[i]) > fn
        close(fn)
}' file1.txt file2.txt

If you want to try this on a Solaris/SunOS system, use /usr/xpg4/bin/awk, /usr/xpg6/bin/awk, or nawk instead of awk.

Note that this script call awk once (no matter how many lines are in file2.txt) rather than calling awk twice and paste once for each line in file2.txt.
This User Gave Thanks to Don Cragun For This Post:
ida1215
# 5  
Old 08-14-2013
Thank you very much for the very clean code and the explanation on my script. My default shell is bash and your code worked perfectly. Smilie

One quick question, what does the following part mean
Code:
f1[++fc1] = $1

bunch of thanks again.
# 6  
Old 08-14-2013
Quote:
Originally Posted by ida1215
Thank you very much for the very clean code and the explanation on my script. My default shell is bash and your code worked perfectly. Smilie

One quick question, what does the following part mean
Code:
f1[++fc1] = $1

bunch of thanks again.
That line creates an array (f1[]) of the values found in the 1st column ($1) of the 1st input file (when FNR {the line number in the of the input lines read from the current file} is equal to NR {the line number of all input lines read from all files}) indexed by the current line number in the file (++fc1). Note that I could have used FNR as the index here, but I need to save the number of lines found in the 1st input file so we can use it in the for loop when we are processing the 2nd input file.
This User Gave Thanks to Don Cragun For This Post:
ida1215
# 7  
Old 08-14-2013
Thanks again for the explanation, Smilie
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