protected function SlopeOneRecommender::computePredictionDatabase in Recommender API 6.2

Overrides Recommender::computePredictionDatabase

1 call to SlopeOneRecommender::computePredictionDatabase()

SlopeOneRecommender::computePrediction in ./Recommender.php

File

./Recommender.php, line 705

Class

SlopeOneRecommender

Slopeone algorihtm. Doesn't support similarity calculation. Only support making predictions.

Code

protected function computePredictionDatabase() {

  // re-create the local variables from class variables.
  $app_id = $this->appId;
  $table_name = $this->tableName;
  $field_mouse = $this->fieldMouse;
  $field_cheese = $this->fieldCheese;
  $field_weight = $this->fieldWeight;
  $created = $this->created;
  $duplicate = $this->duplicate;
  db_query("DELETE FROM {recommender_slopeone_dev} WHERE app_id=%d", $app_id);

  // create dev(i,j)
  db_query("INSERT INTO {recommender_slopeone_dev}(app_id, cheese1_id, cheese2_id, count, dev)\n              SELECT %d, n1.{$field_cheese}, n2.{$field_cheese},\n              COUNT(*), AVG(n1.{$field_weight}-n2.{$field_weight}) FROM {{$table_name}} n1\n              INNER JOIN {{$table_name}} n2 ON n1.{$field_mouse}=n2.{$field_mouse}\n              AND n1.{$field_cheese} <> n2.{$field_cheese}\n              GROUP BY n1.{$field_cheese}, n2.{$field_cheese}", $app_id);

  // create P(u,j)
  if ($this->extension == 'basic') {
    $extension_sql = "AVG(t.{$field_weight}+p.dev)";
  }
  else {
    if ($this->extension == 'weighted') {

      // the 'weighted slope one'
      $extension_sql = "SUM((t.{$field_weight}+p.dev)*p.count)/SUM(p.count)";
    }
  }

  // haven't implemented the "bipolar" extension of Slope One.
  // generate predictions.
  db_query("INSERT INTO {recommender_prediction}(app_id, mouse_id, cheese_id, prediction, created)\n              SELECT %d, t.{$field_mouse}, p.cheese1_id, {$extension_sql}, %d\n              FROM {recommender_slopeone_dev} p INNER JOIN {{$table_name}} t ON p.cheese2_id=t.{$field_cheese}\n              GROUP BY t.{$field_mouse}, p.cheese1_id", $app_id, $created);

  // remove duplicate prediction
  if ($duplicate == 'remove') {
    db_query("DELETE FROM {recommender_prediction} WHERE app_id=%d AND created=%d AND (mouse_id, cheese_id)\n                IN (SELECT {$field_mouse}, {$field_cheese} FROM {{$table_name}})", $app_id, $created);
  }
  $this
    ->purgeOutdatedRecords('prediction');
}