use strict;
use warnings;
use Tk;
use Tk::Canvas;
use Math::FFT;
my $filePath = $ARGV[0] // "testData.txt";
my @data = do { open my $fh, $filePath or die "Can't open $filePath: $!"; local $/; split /\s+/, <$fh> };
my $spectrum;
my $fft = Math::FFT->new(\@data);
$spectrum = $fft->spctrm;
shift @$spectrum; # Remove DC signal component
my $mw = MainWindow->new (-title => "Magnetometer Plotter");
my $canvas = $mw->Canvas (-height => 700, -width => 1024)->pack ();
my $i = 0;
$canvas->createLine(
  (map +(2 + 2 * $i++, $_), NormData($spectrum, 680)), -fill => 'blue'
);
$mw->MainLoop;
sub NormData {
    my ($data, $span) = @_;
    my ($min, $max);
    for my $datum (@$data) {
        $min //= $datum;
        $max //= $datum;
        $min = $datum if $min > $datum;
        $max = $datum if $max < $datum;
    }
    my $scale = $span / ($max - $min);
    map $span - ($_ - $min) * $scale + 10, @$data;
}