Hi Hori,
Please check below for my comments on your code.
On 11 Feb 2013 03:00, "Tiago Hori" <tiago.h...@gmail.com> wrote:
>
> Hi All,
>
> I am trying to force myself to not use one of perl's modules to parse tab
> delimited files (like TXT::CSV), so
Are you referring to module Text::CSV and it's cousin Text::CSV_XS?
please be patient and don't tell me
> just to go and use them. I am trying to re-ivent the wheel, so to speak,
> because as we do with science, we repeat experiments to lean about the
> process even tough we know the outcome.
>
> So I started by putting reading in the files and go one line at time,
> putting those line in arrays and matching a specific line of interest.
With
> join I could then turn the array of interest in a scalar and print that
> out. That is almost what I wanted (see code below):
>
> #! /usr/bin/perl
> use strict;
> use warnings;
>
> my $filename_data = $ARGV[0];
> my $filename_target = $ARGV[1];
> my $line_number = 1;
You really don't need the variable $ line_number within your while loop,
since you could use perl's line number "$."
> my @targets;
>
> open FILE, "<", $filename_data or die $!;
> open TARGET, "<", $filename_target or die $!;
>
It good practice to use lexical variable as filehandles and not BAREWORDs.
Like : open my $ fh,'<', $ filename or die "can't open file:$!";
> while (<TARGET>){
> push (@targets, $_);
This push each of the line with the "\n" into your array.
> }
>
> close (TARGET);
Also, try to check return of the close function on the filehandles.
>
> while (<FILE>){
> chomp;
> my $line = $_;
> my @elements = split ("\t", $line);
> my $row_name = $elements[0];
> if ($line_number == 1){
or if ($. == 1){ # Of course, some may argue that your variable makes
the code, readable.
> my $header = join("\t", @elements);
> print $header, "\n";
> $line_number = 2;}
> elsif($line_number = 2){
Is your file just a 2 line document? If not, what happens if $ line_number
is more than 2? However, if the row you are interested in is just the
second line of your document, then that is ok.
> foreach (@targets){
> chomp;
You probably wouldn't have needed the line above, if you had removed the
new line when populating your array variable in the first place.
> my $target = $_;
> if ($row_name eq $target){
> my $data = join("\t", @elements);
> print $data,"\n";
> }
> }
> }
> }
>
> close (FILE);
>
> Realistic, I don't want the whole row. So I started thinking about how to
> get specific columns. I started reading on the internet and the ideas
seems
> to be placing the arrays containing the lines in a hash indexed by the row
> names. So I did this:
>
> #! /usr/bin/perl
>
> use strict;
> use warnings;
>
> my %hash;
> open FILE, "test.txt" or die $!;
Please stay with the 3 argument for open function.
> my $key;
>
> while (my $line = <FILE>) {
> chomp($line);
> my @array = split("\t", $line);
> $key = shift(@array);
> print $key, "\n";
> push @{ $hash{$key} }, @array;
> }
>
> my $out = join("\t",@{$hash{Row}});
> print $out,"\n";
> print $hash{Row}[1];
>
>
> close FILE;
You are using only one file in your second script.
> That works fine and reads the lines into an array with the elements
> separated into the hash.
>
> So my questions are: is this the best way of accomplishing this two tasks?
> I am really looking for suggestions to improve what I am doing. Is using
> the hashes the best way?
>
> I am have trying to figure out a way of extracting the columns and placing
> them in a hash or a hash of array
Please check the documentation: perldsc. This might help.
or an array. I can't figure out or find
> it in the internet. Can someone give me directions? I am not asking for
> code, but some ideas or some pseudocode would be great!
>
> Thanks!
>
> T.
>
>
> --
> "Education is not to be used to promote obscurantism." - Theodonius
> Dobzhansky.
>
> "Gracias a la vida que me ha dado tanto
> Me ha dado el sonido y el abecedario
> Con él, las palabras que pienso y declaro
> Madre, amigo, hermano
> Y luz alumbrando la ruta del alma del que estoy amando
>
> Gracias a la vida que me ha dado tanto
> Me ha dado la marcha de mis pies cansados
> Con ellos anduve ciudades y charcos
> Playas y desiertos, montañas y llanos
> Y la casa tuya, tu calle y tu patio"
>
> Violeta Parra - Gracias a la Vida
>
> Tiago S. F. Hori. PhD.
> Ocean Science Center-Memorial University of Newfoundland
