use strict;
use warnings;
use PDL;
use PDL::FFTW3;
use PDL::Graphics::Simple;
my $filePath = $ARGV[0] // "testData.txt";
my @data = do { open my $fh, $filePath or die "Can't open $filePath: $!"; local $/; split /\s+/, <$fh> };

sub spectrum {my ($d)=@_;
  my $hn=$d->dim(0)-1;
  my $a2=$d->abs2/(($hn*2)**2);
  $a2->slice([1,$hn-1])*=2;
  $a2;
}
my $spectrum = spectrum(rNfft1 pdl(\@data));
$spectrum = $spectrum->slice('1:-1'); # Remove DC signal component

line pdl($spectrum);
print "ret> "; <STDIN>;