perform calculations on cells in csv file

[gsaray101]

there is a csv file like this:
date, val1, val2, val3, val4 etc
1/2/2007, 1, 4, 5, 6
1/3/2007, 2, 5, 7, 10
1/5/2007, 5, 6, 8, 11

what I need to do is, calculate the differnce between cells for each column and write it to a file. for example, since there is no previous value to row one, write first row to a file. then subtrack second raw values from the first row values and write the output to the second line in ouptput file - (2-1, 5-4, 7-5, 10, 6). Third raw in the output file should be, 5-2, 6-5, 8-7, 11-10 and so on. Can anybody help me with this?

[KevinADC]

Please post what you have tried so far.

[gsaray101]

I dont even know how to start this

[numberwhun]

Well, if that is the case, I would have to ask how much Perl experience do you have? Do you know how to work with modules?

I am asking because there is a perl module that falls under the DBI module family called DBD::CSV, that allows you to interact with a CSV file as if it were a database. Take a read of that page to find out about it.

If you don't have much Perl experience, I would definitely run down to your local Barnes & Noble and pick up "Learning Perl, 4th Edition" as it is a great starter book.

Regards,

Jeff

[gsaray101]

I have little experience with perl. I was thinking about making an array, read the lines into an array and try to subtrack the numbers like that but it may need to be two dimensional arrays.

[gsaray101]

#!/usr/local/bin/perl
 
use Data::Dumper;
 
open(FILE,"<test.csv");
$row=-1;$col=-1;
while (<FILE>) {
    chomp;
    if (/^[0-9]/) {
        chomp;
        $row++;
        $col = -1;
 
        foreach $char (split /,/) {
            $col++;
            $cell[$row][$col]=$char;
        }
    }
}
 
for $i (0..$#cell) {
    $aref = $cell[$i];
    $n = @$aref - 1;
    for $j (0..$n) {
        print "$cell[$i][$j],";
    }
    print "\n";
}
 

basically, I have the information in the two dimensional array now. what I need to do is to the subtrack the symetic cells from each other. First column is the time stamp and needs to be left alone.

[gsaray101]

there is a csv file like this:
date, val1, val2, val3, val4 etc
1/2/2007, 1, 4, 5, 6
1/3/2007, 2, 5, 7, 10
1/5/2007, 5, 6, 8, 11

what I need to do is, calculate the differnce between cells for each column and write it to a file. for example, since there is no previous value to row one, write first row to a file. then subtrack second raw values from the first row values and write the output to the second line in ouptput file - (2-1, 5-4, 7-5, 10, 6). Third raw in the output file should be, 5-2, 6-5, 8-7, 11-10 and so on. Can anybody help me with this?

I have this code so far.

#!/usr/local/bin/perl 
use Data::Dumper; 
open(FILE,"<test.csv"); 
 
$row=-1;$col=-1; 
while (<FILE>) { 
    chomp; 
    if (/^[0-9]/) { 
        chomp; 
        $row++; 
        $col = -1; 
        foreach $char (split /,/) { 
            $col++; 
            $cell[$row][$col]=$char; 
        } 
    } 
} 
 
for $i (0..$#cell) { 
    $aref = $cell[$i]; 
    $n = @$aref - 1; 
    for $j (0..$n) { 
        print "$cell[$i][$j],"; 
    } 
    print "\n"; 
}
 

[miller]

Please do not double post your question. I've merged the two threads for you.

- MODERATOR