Uniquify a column based on values of another column 1

[johnsbn]

Hello,

I'm a perl newbie and would appreciate your help here.

This is the file I have,

Arm -0.4 1.2 3.2
Bow 0.06 2.3 4.9
Arm 0.1 4.9 31.0
Pix -0.7 45.6 33.0
Gel 1.0 12.0 3.2
Arm 1.1 1.9 3.0

My columns of interest are 1 and 4. I want to uniquify column1 entries based on its largest column 4 value.

The new file should have the following,

Bow 0.06 2.3 4.9
Arm 0.1 4.9 31.0
Pix -0.7 45.6 33.0
Gel 1.0 12.0 3.2

 

[prex1]

What have you tried so far?

Franco

http://www.xcalcs.com

: Online engineering calculations

http://www.megamag.it

: Magnetic brakes for fun rides

http://www.levitans.com

: Air bearing pads

 

[johnsbn]

This is what I've tried so far. Please help.


sub comp()
{
if ($field1 != 0)
{
while (<IN_FILE>)
{
chomp;
$next_line = $_;
($next_name,$next_field2,$next_field3,$next_field4) = split(/\s+/,$next_line);

if ($field1 eq $next_name)
{
if ($next_field4 > $field4)
{
$field4 = $next_field4;
$field2 = $next_field2;
$field3 = $next_field3;
}
}
print OUTFILE "$field1 $field2 $field3 $field4\n";
}

}

}

while (<IN_FILE>)
{
chomp;
@data = <IN_FILE>;
&comp;
($field1,$field2,$field3,$field4) = split(/\s+/,$data);

}

 

[Annihilannic]

You have to open a file before you can read it.

You are reading the file in multiple places... remember that there is only one file handle, and the file is read sequentially, so you are going to get different parts of the file read in different sections of code. Just read the file once in one place, and store it in a hash.

Personally I would use the following algorithm:

while lines remain
    read a line
    split into fields
    if the last field is larger than those previously seen for this record type (or if it is the first record of this type)
        save the field value in a hash of the largest values indexed by record type
        save the entire line in a hash of the data indexed by record type
    end if
end while

print out the values of the data hash

Annihilannic.

 

[johnsbn]

I opened the file at the begining of the code. Sorry, I didn't post those lines here.

In your alogirthm,

if the last field is larger than those previously seen for this record type (or if it is the first record of this type)
save the field value in a hash of the largest values indexed by record type
save the entire line in a hash of the data indexed by record type

Can you give an example for this hash? I'm not proficient in using hashes, yet.

Thanks,
John

 

[Annihilannic]

[gray]#!/usr/bin/perl -w[/gray]

[url=http://perldoc.perl.org/functions/use.html][black][b]use[/b][/black][/url] [green]strict[/green][red];[/red]

[url=http://perldoc.perl.org/functions/my.html][black][b]my[/b][/black][/url] [blue]%largest[/blue][red];[/red]
[black][b]my[/b][/black] [blue]%data[/blue][red];[/red]

[olive][b]while[/b][/olive] [red]([/red]<>[red])[/red] [red]{[/red]
        [black][b]my[/b][/black] [blue]@fields[/blue]=[url=http://perldoc.perl.org/functions/split.html][black][b]split[/b][/black][/url][red];[/red]
        [olive][b]if[/b][/olive] [red]([/red]![url=http://perldoc.perl.org/functions/defined.html][black][b]defined[/b][/black][/url] [blue]$largest[/blue][red]{[/red][blue]$fields[/blue][red][[/red][fuchsia]0[/fuchsia][red]][/red][red]}[/red] || [blue]$fields[/blue][red][[/red][fuchsia]3[/fuchsia][red]][/red] > [blue]$largest[/blue][red]{[/red][blue]$fields[/blue][red][[/red][fuchsia]0[/fuchsia][red]][/red][red]}[/red][red])[/red] [red]{[/red]
                [blue]$largest[/blue][red]{[/red][blue]$fields[/blue][red][[/red][fuchsia]0[/fuchsia][red]][/red][red]}[/red] = [blue]$fields[/blue][red][[/red][fuchsia]3[/fuchsia][red]][/red][red];[/red]
                [blue]$data[/blue][red]{[/red][blue]$fields[/blue][red][[/red][fuchsia]0[/fuchsia][red]][/red][red]}[/red] = [blue]$_[/blue][red];[/red]
        [red]}[/red]
[red]}[/red]

[url=http://perldoc.perl.org/functions/print.html][black][b]print[/b][/black][/url] [url=http://perldoc.perl.org/functions/values.html][black][b]values[/b][/black][/url] [blue]%data[/blue][red];[/red]

Annihilannic.

 

[johnsbn]

Thanks Ann.