Examples of PreferenceTransform

org.apache.mahout.cf.taste.transforms.PreferenceTransform

Implementations encapsulate a transform on a {@link Preference}'s value. These transformations are typically applied to values before they are used to compute a similarity value. They are typically not applied elsewhere; in particular {@link org.apache.mahout.cf.taste.model.DataModel}s no longer use a transform like this to transform all of their preference values at the source.

Examples of org.apache.mahout.cf.taste.transforms.PreferenceTransform

  }


  @Test
  public void testStdev() throws Exception {
    DataModel dataModel = getDataModel(new long[] {1}, new Double[][] {{-1.0,-2.0}});
    PreferenceTransform zScore = new ZScore(dataModel);
    assertEquals(Math.sqrt(2.0)/2.0, zScore.getTransformedValue(new GenericPreference(1, 0, -1.0f)), EPSILON);
    assertEquals(-Math.sqrt(2.0)/2.0, zScore.getTransformedValue(new GenericPreference(1, 1, -2.0f)), EPSILON);
  }

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Examples of org.apache.mahout.cf.taste.transforms.PreferenceTransform

  }


  @Test
  public void testExample() throws Exception {
    DataModel dataModel = getDataModel(new long[] {1}, new Double[][] {{5.0, 7.0, 9.0}});
    PreferenceTransform zScore = new ZScore(dataModel);
    assertEquals(-1.0, zScore.getTransformedValue(new GenericPreference(1, 0, 5.0f)), EPSILON);
    assertEquals(0.0, zScore.getTransformedValue(new GenericPreference(1, 1, 7.0f)), EPSILON);
    assertEquals(1.0, zScore.getTransformedValue(new GenericPreference(1, 2, 9.0f)), EPSILON);
  }

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