Percentile.pm

package App::RecordStream::Aggregator::Percentile;

our $VERSION = "4.0.3";

use strict;
use warnings;

use App::RecordStream::Aggregator::InjectInto::Field;
use App::RecordStream::DomainLanguage::Registry;

use base qw(App::RecordStream::Aggregator::InjectInto::Field);

sub new
{
  my $class      = shift;
  my $percentile = shift;
  my $field      = shift;

  my $this = $class->SUPER::new($field);
  $this->{'percentile'} = $percentile;

  return $this;
}

sub new_from_valuation
{
  my $class      = shift;
  my $percentile = shift;
  my $valuation  = shift;

  my $this = $class->SUPER::new_from_valuation($valuation);
  $this->{'percentile'} = $percentile;

  return $this;
}

sub initial {
  return [];
}

sub combine_field
{
  my $this   = shift;
  my $cookie = shift;
  my $value  = shift;

  push @$cookie, $value;
  return $cookie;
}

sub squish
{
  my $this   = shift;
  my $cookie = shift;

  my $percentile = $this->{'percentile'};

  my @sorted = sort { $a <=> $b } @$cookie;

  my $index = int( (scalar @sorted) * ($percentile / 100));

  if ( $index == scalar @sorted )
  {
    $index--;
  }

  return $sorted[$index];
}

sub short_usage
{
  return "value of pXX for field";
}

sub long_usage
{
  print <<EOF;
Usage: per,<percentile>,<field>
   Finds the field value which <percentile> percent of values are less than.

   This is computed by creating an array of all values, sorting, and indexing into it at the
   floor((percentile / 100) * length) point
EOF
}

sub argct
{
  return 2;
}

App::RecordStream::Aggregator->register_implementation('percentile', __PACKAGE__);
App::RecordStream::Aggregator->register_implementation('perc', __PACKAGE__);

App::RecordStream::DomainLanguage::Registry::register_vfn(__PACKAGE__, 'new_from_valuation', 'percentile', 'SCALAR', 'VALUATION');
App::RecordStream::DomainLanguage::Registry::register_vfn(__PACKAGE__, 'new_from_valuation', 'perc', 'SCALAR', 'VALUATION');

1;