读取 perl 中的特定列

Question

我是 perl 新手。我有下面的文本文件，从那里我只想要一个 Time 列，下一列是值。如何在 perl 中创建带有我想要的输出的文本文件。

Time  Value    Time    Value    Time    Value
1   0.353366497 1   0.822193251 1   0.780866396
2   0.168834182 2   0.865650713 2   0.42429447
3   0.323540698 3   0.865984245 3   0.856875894
4   0.721728497 4   0.634773162 4   0.563059042
5   0.545131335 5   0.029808531 5   0.645993399
6   0.143720835 6   0.949973296 6   0.14425803
7   0.414601876 7   0.53421424  7   0.826148814
8   0.194818367 8   0.942334356 8   0.837107013
9   0.291448263 9   0.242588271 9   0.939609775
10  0.500159997 10  0.428897293 10  0.41946448 

我试过下面的代码：

use strict;
use warnings;
use IO::File;
my $result;
my @files = (q[1.txt],q[2.txt],q[3.txt]);
my @fhs = ();
foreach my $file (@files) { 
    my $fh = new IO::File $file, O_RDONLY;
    push @fhs, $fh if defined $fh;
} 

while(1) { 
    my @lines = map { $_->getline } @fhs;
    last if grep { not defined $_ } @lines[0..(@fhs-1)];
    my @result=join(qq[\t], map { s/[\r?\n]+/ /g; $_ } @lines ) . qq[\r\n];
    open (MYFILE, '>>Result.txt');
    print (MYFILE "@result");
    close (MYFILE);
}

Answer 1

我会选择split。

use warnings;
use strict;

open (my $f, '<', 'your-file.dat') or die;

while (my $line = <$f>) {
  my @elems = split ' ', $line;
  print join "\t", @elems[0,1,3,5];
  print "\n";
}

Answer 2

这是一个单行；无需编写脚本：

$ perl -lanE '$,="\t"; say @F[0,1,3,5]' 1.txt 2.txt 3.txt

如果你喜欢，你可以把它缩短为：

$ perl -lanE '$,="\t"; say @F[0,1,3,5]' [123].txt

Answer 3

现在，您只是将文件的行连接在一起。如果这不能为您提供您喜欢的输出，您需要删除一些列。

由于您的输出看起来像是有制表符分隔的文件作为输入，因此我将输入的行拆分为制表符。而且由于您只想要第二列，因此我只在拆分的第一个偏移量处取列。

my $line_num = 0;
while(1) {
    my @lines = map { $_->getline } @fhs;
    last if grep { not defined $_ } @lines[0..$#fhs];
    $line_num++;
    my @rows     = map { [ split /\t/ ] } @lines;
    my $time_val = $rows[0][0];
    die "Time values are not all equal on line #$line_num!" 
        if grep { $time_val != $_->[0] } @rows
        ;
    my $result = join( q[\t], $time_val, map { $_->[1] } @rows );
    open (MYFILE, '>>Result.txt');
    print (MYFILE "$result\n");
    close (MYFILE);
}

当然，没有理由进行自定义编码来拆分分隔列：

use Text::CSV; 
...
my $csv  = Text::CSV->new( { sep_char => "\t" } );

while(1) { 
    my @rows = map { $csv->getline( $_ ) } @fhs;
    last if grep { not defined $_ } @rows[0..$#fhs];
    my ( $time_val, @time_vals ) = map { $_->[0] } @rows;
    my @values = map { $_->[1] } @rows;
    die "Time values are not all equal on line #$line_num!" 
        if grep { $time_val != $_ } @time_vals
        ;
    my $result = join( q[\t], $time_val, @values );
    ...
}

Answer 4

    use strict;    
use warnings;    
open(FH,"<","a.txt");    
print "=========== A File content =========== \n";    
my $a = `cat a.txt`; 
print "$a\n";  

my @temp = <>;  

    my (@arr, @entries, @final);  
    foreach ( @temp ) {  
         @arr = split ( " ", $_ );  
         push @entries, @arr;  
}  
close FH;

my @entries1 = @entries;  

for(my $i = 7; $i<=$#entries; $i=$i+2) {  

        push @final, $entries[$i];
}

my $size = scalar @final;

open FH1, ">", "b.txt";  
print FH1 "Time \t Value\n";  
for(my $i = 0; $i < $size; $i++) {  

        my $j = $i+1;  
        print FH1 "$j \t $final[$i]\n";  
}

close FH1;    

print "============ B file content ===============\n";    
my $b = `cat b.txt`;    
print "$b";


O/P:    
=========== A File content ===========  
Time  Value    Time    Value    Time    Value    
1   0.353366497 1   0.822193251 1   0.780866396   
2   0.168834182 2   0.865650713 2   0.42429447  
3   0.323540698 3   0.865984245 3   0.856875894  
4   0.721728497 4   0.634773162 4   0.563059042  
5   0.545131335 5   0.029808531 5   0.645993399  
6   0.143720835 6   0.949973296 6   0.14425803  
7   0.414601876 7   0.53421424  7   0.826148814  
8   0.194818367 8   0.942334356 8   0.837107013  
9   0.291448263 9   0.242588271 9   0.939609775  
10  0.500159997 10  0.428897293 10  0.41946448  

============ B file content ===============  
Time     Value  
1        0.353366497  
2        0.822193251  
3        0.780866396  
4        0.168834182  
5        0.865650713  
6        0.42429447  
7        0.323540698  
8        0.865984245  
9        0.856875894  
10       0.721728497  
11       0.634773162  
12       0.563059042  
13       0.545131335  
14       0.029808531  
15       0.645993399  
16       0.143720835  
17       0.949973296  
18       0.14425803  
19       0.414601876   
20       0.53421424  
21       0.826148814  
22       0.194818367  
23       0.942334356  
24       0.837107013  
25       0.291448263  
26       0.242588271  
27       0.939609775  
28       0.500159997  
29       0.428897293  
30       0.41946448