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55 lines
1.3 KiB
Perl
Executable File
55 lines
1.3 KiB
Perl
Executable File
#!/usr/bin/env perl
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use feature say;
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use utf8;
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use PDL;
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use PDL::FFT;
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use PDL::IO::Misc;
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my $twoPI = 2*3.1415926539;
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# space parameters
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our $Δt=.001;
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our $xmin = 0;
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our $xmax = 250;
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our $num_bins = ($xmax-$xmin)/$Δt;
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say "Creating $num_bins bins";
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# Complex Number z(x) = u(x) + iv(x)
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my @th_list=tophat(10,7);
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my $u = pdl(@th_list);
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my $v = zeroes($u);
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# Output time-domain tophat
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open $tophattab, '>', 'analyses/tables/tophat.tab';
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for ($i=0; $i < $num_bins; $i++) {
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my $x_coord = ($xmax-$xmin)*($i/$num_bins) + $xmin;
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say $tophattab "$x_coord $th_list[$i]";
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}
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close $tophattab;
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# Transform z(x) to z(1/x) = u(1/x) + iv(1/x)
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fft($u,$v);
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# Determine frequency coordinates
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my $num_elements = nelem($u);
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say "Found $num_elements elements.";
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$f = $u->xlinvals(-($num_elements/2-1)/$num_elements/$Δt,1/2/$Δt)->rotate(-($num_elements/2 -1));
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my $φdiff = atan2($v,$u);
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my $timelag = $φdiff/($twoPI*$f);
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wcols $f,$timelag,'analyses/tables/tophat_fft.tab';
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sub tophat {
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(my $mean,my $width) = @_;
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my $halfwidth = $width/2;
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my @vals = ();
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for ($i=0; $i < $num_bins; $i++) {
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my $x_coord = ($xmax-$xmin)*($i/$num_bins) + $xmin;
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if ($x_coord >= ($mean - $halfwidth ) && $x_coord <= ($mean + $halfwidth)) { push @vals, 1/$width; }
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else { push @vals, 0; }
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}
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return @vals;
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} |