Solved

multiplying or dividing all values in the last column of a file using one liner perl script in linux

Posted on 2011-09-20
7
330 Views
Last Modified: 2012-05-12
I'm using the code below to add or subtract values from each value in the last column of data in a 4 column file (see attached). Instead of adding/subtracting how would I divide or multiply? Would be as simply as replacing the the minus with a * or / next to the number I wanted the value mutliplied or divided by?

[user@server ~]$ perl -alne 'BEGIN{$i=pop}($F[3]+=$i)>0 or $F[3]=0; print "@F"' file1.txt -0.468 > file1b.txt

Open in new window

0
Comment
Question by:libertyforall2
  • 3
  • 2
  • 2
7 Comments
 
LVL 84

Expert Comment

by:ozo
ID: 36571052
yes
0
 

Author Comment

by:libertyforall2
ID: 36571090
Ok. One more quick question. I just realized I will need to add/subtract a value if the data point is zero else multiply/divide by a different value. Lets say add 3.2 if zero else divide by .8 for all values in the final column.
0
 
LVL 12

Accepted Solution

by:
tel2 earned 250 total points
ID: 36572869
Hi lfa2,

Regarding your first question, if you're asking if you could do this:
    perl -alne 'BEGIN{$i=pop}($F[3]+=$i)>0 or $F[3]=0; print "@F"' file1.txt *0.468 > file1b.txt
and this:
    perl -alne 'BEGIN{$i=pop}($F[3]+=$i)>0 or $F[3]=0; print "@F"' file1.txt /0.468 > file1b.txt
then my answer would be: No.  I think that argument after the input file (e.g. -0.468) must be just a number (which can be +ve or -ve), otherwise I think you'd be doing maths like:
  $F[3]+=/.8    (ie: $F[3] = $F[3] + /.8)
which doesn't make sense to me.

For your second question, does this work for you?:
    perl -alne 'BEGIN{$mult=pop;$add=pop};$F[3] = ($F[3]==0 ? eval("$F[3]$add") : eval("$F[3]$mult")); print "@F"' file1.txt +3.2 /.8 >file1b.txt
0
Free Tool: Site Down Detector

Helpful to verify reports of your own downtime, or to double check a downed website you are trying to access.

One of a set of tools we are providing to everyone as a way of saying thank you for being a part of the community.

 
LVL 84

Assisted Solution

by:ozo
ozo earned 250 total points
ID: 36573004
perl -alne 'BEGIN{$i=pop}if($F[3]){$F[3]+=3.2}else{$F[3]/=$i}; print "@F"' file1.txt .8 > file1b.txt
0
 
LVL 12

Expert Comment

by:tel2
ID: 36576909
As you may have noticed lfa2, my solutions assume you want to supply the +3.2 and /.8 as arguments (i.e. after the code):

Here's a slightly more efficient one (the 1st "eval" was not needed):
    perl -alne 'BEGIN{$mult=pop;$add=pop};$F[3] = $F[3]==0 ? $F[3]+=$add : eval "$F[3]$mult"; print "@F"' file1.txt -3.2 /.8 >file1b.txt

And if you are always going to be dividing (never multiplying), it could be further simplified to:
    perl -alne 'BEGIN{$div=pop;$add=pop}$F[3] = $F[3]==0 ? $F[3]+$add : $F[3]/$div; print "@F"' file1.txt +3.2 .8 >file1b.txt

Which can be compressed to:
    perl -alne 'BEGIN{$d=pop;$a=pop}$F[3]=$F[3]==0?$F[3]+$a:$F[3]/$d;print"@F"' file1.txt +3.2 .8

Or if you're always going to be multiplying:
    perl -alne 'BEGIN{$m=pop;$a=pop}$F[3]=$F[3]==0?$F[3]+$a:$F[3]*$m;print"@F"' file1.txt +3.2 1.25
As you can see, I'm multiplying by 1.25, which is the same as dividing by .8.
0
 
LVL 12

Expert Comment

by:tel2
ID: 36576924
Append:
  >file1b.txt
to my last 2 solutions, pls lfa2.
0
 

Author Closing Comment

by:libertyforall2
ID: 36584610
Works
0

Featured Post

Networking for the Cloud Era

Join Microsoft and Riverbed for a discussion and demonstration of enhancements to SteelConnect:
-One-click orchestration and cloud connectivity in Azure environments
-Tight integration of SD-WAN and WAN optimization capabilities
-Scalability and resiliency equal to a data center

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

A short article about a problem I had getting the GPS LocationListener working.
In this post we will learn how to connect and configure Android Device (Smartphone etc.) with Android Studio. After that we will run a simple Hello World Program.
In this fifth video of the Xpdf series, we discuss and demonstrate the PDFdetach utility, which is able to list and, more importantly, extract attachments that are embedded in PDF files. It does this via a command line interface, making it suitable …

828 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question