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Re: 2D binning

by spx2 (Deacon)
on Feb 19, 2010 at 00:08 UTC ( #824067=note: print w/replies, xml ) Need Help??


in reply to 2D binning

much more efficient would be to divide the coordinates length by the bin side and round that off and concatenate those together and they form a pretty good hash key(and you don't need to compute minimum or maximum any more). but here's a solution following your line of thought:
use strict; use warnings; use List::AllUtils qw/minmax/; my @points = ( [3.70722,0.54617,], [3.67342,0.64892,], [3.75017,0.85075,], [3.82831,0.83506,], [3.71852,0.79251,], [3.80706,0.70426,], [3.91839,0.94094,], [3.90726,0.81722,], [3.89007,0.76107,], [3.98006,0.62477,], ); my $bins; my $binside = 0.1; my ($xmin,$xmax) = minmax( map { $_->[0] } @points ); my ($ymin,$ymax) = minmax( map { $_->[1] } @points ); for( my $xbin=$xmin ; $xbin<=$xmax ; $xbin+= $binside) { for(my $ybin=$ymin ; $ybin<=$ymax ; $ybin+= $binside) { my $p = $points[0]; if( $p->[0] >= $xbin && $p->[0] < $xbin + $binside && $p->[1] >= $ybin && $p->[1] < $ybin + $binside ) { $bins->{$xbin.$ybin} = [] unless($bins->{$xbin.$ybin}); push @{ $bins->{$xbin.$ybin} } , (shift @points); }; } } print scalar(keys(%$bins)); 4
this sounds a lot like the bin packing problem.

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Re^2: 2D binning
by austinby (Initiate) on Feb 19, 2010 at 13:32 UTC
    Thanks a lot for your input monks,
    I'll test all your ideas and send updates.
    Austin-
      Hi perlmonks,
      I tested the code sent by spx2 and BrowserUk after installing the List::AllUtils and Data::Dump modules.
      I get "4" as output from spx2's code.
      #!/usr/bin/perl -slw use strict; use warnings; use List::AllUtils qw/minmax/; my @points = ( [3.70722,0.54617,], [3.67342,0.64892,], [3.75017,0.85075,], [3.82831,0.83506,], [3.71852,0.79251,], [3.80706,0.70426,], [3.91839,0.94094,], [3.90726,0.81722,], [3.89007,0.76107,], [3.98006,0.62477,], ); my $bins; my $binside = 0.1; my ($xmin,$xmax) = minmax( map { $_->[0] } @points ); my ($ymin,$ymax) = minmax( map { $_->[1] } @points ); for( my $xbin=$xmin ; $xbin<=$xmax ; $xbin+= $binside) { for(my $ybin=$ymin ; $ybin<=$ymax ; $ybin+= $binside) { my $p = $points[0]; if( $p->[0] >= $xbin && $p->[0] < $xbin + $binside && $p->[1] >= $ybin && $p->[1] < $ybin + $binside ) { $bins->{$xbin.$ybin} = [] unless($bins->{$xbin.$ybin}); push @{ $bins->{$xbin.$ybin} } , (shift @points); }; } } print scalar(keys(%$bins));
      Not sure what the "4" means.

      I get a "Global symbol "$Y" requires explicit package name at line " error with BrowserUk's code. When I change the positions of $Y and $X, I get a "Global symbol "$X" requires explicit package name at line "
      #!/usr/bin/perl -slw use strict; use List::Util qw[ sum ]; use Data::Dump qw[ pp ]; our $Y //= 10; our $X //= 10; my @xs = map -3+rand 6, 1 .. $X; my @ys = map -3+rand 6, 1 .. $Y; my %bins; for my $x ( @xs ) { my $xc = ( int( $x * 10 ) + 0.5 ) / 10; for my $y ( @ys ) { my $yc = ( int( $y * 10 ) + 0.5 ) / 10; ++$bins{ "$xc:$yc" }; } } pp \%bins; printf "Buckets used: %d, total values %d \n", scalar keys %bins, sum values %bins;
      There's a script online that does exactly what I'm trying to do (http://homepages.ulb.ac.be/~dgonze/SCRIPTS/PERL/histogram-2d.pl), but requires user-defined inputs. I'd like to do this such that all the user needs is the input file.

        You must be using a pre-5.10 version of Perl. Try:

        #!/usr/bin/perl -slw use strict; use Data::Dump qw[ pp ]; our $Y ||= 10; ## changed from //= for pre-5.10 our $X ||= 10; my @xs = map -3+rand 6, 1 .. $X; my @ys = map -3+rand 6, 1 .. $Y; my %bins; for my $x ( @xs ) { my $xc = ( int( $x * 10 ) + 0.5 ) / 10; for my $y ( @ys ) { my $yc = ( int( $y * 10 ) + 0.5 ) / 10; ++$bins{ "$xc:$yc" }; } } pp \%bins; printf "Buckets used: %d, total values %d \n", scalar keys %bins, sum values %bins;

        You can vary the number of datapoints generated by using a command line like:

        perl -s theScript.pl -X=100 -Y=100

        Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error.
        "Science is about questioning the status quo. Questioning authority".
        In the absence of evidence, opinion is indistinguishable from prejudice.
        4 is the number of bins. do you need the contents of the bins ? also , the code at the link you indicated is ancient Perl4 code, you don't want to use that.

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