Re: column counter and printf question

Perl can count the columns.

use strict;
use warnings;

while( my $line = <DATA>) {
  next unless $. > 12;     # $. contains current line number
  next if $line =~ /^$/;      # skip blank lines
  chomp $line;            # remove end-of-line character
  $line =~ s/\s+//;       # strip leading whitespace
  
  my @columns = split(/\s+/, $line);    # split columns on whitespace
  my $format = "%8.3f" . "%10.3f"x(@columns-3) . "\n";
  printf $format, @columns[2..$#columns];
}

# my guess at the input data
__DATA__
SKIP 1
SKIP 2
SKIP 3
SKIP 4
SKIP 5
SKIP 6
SKIP 7
SKIP 8
SKIP 9
SKIP 10
SKIP 11
SKIP 12
Line_1 0.0 0.0 1.0 2.0 3.0 4.0 5.0 6.0 7.0 8.0
Line_2 0.0 0.0 2.0 3.0 4.0 5.0 6.0 7.0 8.0 9.0
Line_3 0.0 0.0 3.0 4.0 5.0 6.0 7.0 8.0 9.0 1.0
Line_4 0.0 0.0 4.0 5.0 6.0 7.0 8.0 9.0 1.0 2.0
Line_5 0.0 0.0 5.0 6.0 7.0 8.0 9.0 1.0 2.0 3.0
[download]

Bill

Comment on Re: column counter and printf question Download Code

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Re^2: column counter and printf question by Anonymous Monk on Oct 28, 2015 at 15:30 UTC
`$line =~ s/\s+//; # strip leading whitespace` The comment doesn't match the code, it strips the first whitespace it finds. Or perhaps you're missing a `^`.	[reply] [d/l] [select]
Re^3: column counter and printf question by scorpio17 (Canon) on Oct 28, 2015 at 17:23 UTC
Oops... thank you. I've corrected that.	[reply]
Re^2: column counter and printf question by fasoli (Beadle) on Oct 28, 2015 at 15:53 UTC
Hi and thanks for the help, Can you explain something from this bit `my $format = "%8.3f" . "%10.3f"x(@columns-3) . "\n";` Why "@columns-3", what does the "-3" mean? Also, what does "x" mean there? Literally, how many times to repeat the format?	[reply] [d/l]
Re^3: column counter and printf question by BillKSmith (Monsignor) on Oct 28, 2015 at 20:51 UTC
A printf format is a perl string. In this case, it is constructed using perl's string operators. The dot ('.') is the concatenation operator. The 'x' is the repetition operator (Refer to Multiplicative Operators section of perlop). The specification '10.3f' is repeated @columns-3 times where @columns is the total number of columns. (The three comes from the fact that the first two columns are not printed and the third has it own format specification) Bill	[reply]
Re^4: column counter and printf question by fasoli (Beadle) on Oct 29, 2015 at 12:22 UTC
Hi Bill, Thanks for the reply and the link, I get it now. Although one more question, should (@columns-3) maybe be ($columns-3)? Also, I'm a bit confused over the fact that the following pieces of code produce different output files. Can you take a look at the scripts and let me know where the problem is, as I can't understand it? `#/bin/perl/ use strict; use warnings; open my $input, '<', './2kc29-out.txt' or die $!; open my $output, '>', 'test_thu1.txt' or die $!; while (my $line = <$input>) { chomp $line; $line =~ s/^\s+//; next if 1 .. $line =~ /\@TYPE xy/; #perlop range operators my @columns = split(/\s+/, $line); my $format = "%8.3f" . "%10.3f"x(@columns-3) . "\n"; printf $output $format, @columns[2..$#columns]; }` [download] and the second one: #/bin/perl/ use strict; use warnings; open my $input, '<', './2kc29-out.txt' or die $!; open my $output, '>', 'test_thu2.txt' or die $!; while (my $line = <$input>) { chomp $line; $line =~ s/^\s+//; next if 1 .. $line =~ /\@TYPE xy/; #perlop range operators my @columns = split /\s+/, $line; my $col1 = shift@columns; # column 1 (ignore) my $col2 = shift@columns; # column 2 (ignore) my $col3 = shift@columns; # column 3 (keep) my $result = printf $output ("%8.3f",$col3); # column 3 format # loop over remaining columns for my $c (@columns) { my $data = printf $output ("%10.3f",$c); $result .= " $data"; # append $result } printf $output "$result\n"; } [download] The second script, prints a slightly bigger file (37.51MB over 31,28MB) because in the output it has printed dozens of random "1" numbers right after the last column. Why is this happening?	[reply] [d/l] [select]
Re^5: column counter and printf question by Athanasius (Cardinal) on Oct 29, 2015 at 12:53 UTC
Re^6: column counter and printf question by fasoli (Beadle) on Oct 29, 2015 at 14:45 UTC
Re^5: column counter and printf question by GotToBTru (Prior) on Oct 29, 2015 at 14:45 UTC
Re^3: column counter and printf question by ww (Archbishop) on Oct 28, 2015 at 18:25 UTC
Second of your questions in this thread that's easily answered from the docs which came with your distribution. See `perldoc perldoc` et seq. Spirit of the Monastery	[reply] [d/l]