Pearson Class Reference
Shrunk Pearson correlation for rating data.
More...
List of all members.
Public Member Functions |
void | AddEntity (int entity_id) |
| Add an entity to the CorrelationMatrix by growing it to the requested size.
|
override void | ComputeCorrelations (IRatings ratings, EntityType entity_type) |
| Compute correlations for given ratings.
|
int[] | GetNearestNeighbors (int entity_id, uint k) |
| Get the k nearest neighbors of a given entity.
|
IList< int > | GetPositivelyCorrelatedEntities (int entity_id) |
| Get all entities that are positively correlated to an entity, sorted by correlation.
|
| Pearson (int num_entities) |
| Constructor. Create a Pearson correlation matrix.
|
double | SumUp (int entity_id, ICollection< int > entities) |
| Sum up the correlations between a given entity and the entities in a collection.
|
void | Write (StreamWriter writer) |
| Write out the correlations to a StreamWriter.
|
Static Public Member Functions |
static float | ComputeCorrelation (IRatings ratings, EntityType entity_type, IList< Pair< int, float >> entity_ratings, int j, float shrinkage) |
| Compute correlation between two entities for given ratings.
|
static float | ComputeCorrelation (IRatings ratings, EntityType entity_type, int i, int j, float shrinkage) |
| Compute correlation between two entities for given ratings.
|
static CorrelationMatrix | Create (int num_entities) |
| Creates a correlation matrix.
|
static CorrelationMatrix | Create (IRatings ratings, EntityType entity_type, float shrinkage) |
| Create a Pearson correlation matrix from given data.
|
static CorrelationMatrix | ReadCorrelationMatrix (StreamReader reader) |
| Creates a CorrelationMatrix from the lines of a StreamReader.
|
Protected Attributes |
int | num_entities |
| Number of entities, e.g. users or items.
|
Properties |
override bool | IsSymmetric [get] |
| returns true if the matrix is symmetric, which is generally the case for similarity matrices
|
float | Shrinkage [get, set] |
| shrinkage parameter, if set to 0 we have the standard Pearson correlation without shrinkage
|
Detailed Description
Shrunk Pearson correlation for rating data.
The correlation values are shrunk towards zero, depending on the number of ratings the estimate is based on. Otherwise, we would give too much weight to similarities estimated from just a few examples.
http://en.wikipedia.org/wiki/Pearson_correlation
We apply shrinkage as in formula (5.16) of chapter 5 of the Recommender Systems Handbook. Note that the shrinkage formula has changed betweem the two publications. It is now based on the assumption that the true correlations are normally distributed; the shrunk estimate is the posterior mean of the empirical estimate.
Literature:
Constructor & Destructor Documentation
Pearson |
( |
int |
num_entities |
) |
[inline] |
Constructor. Create a Pearson correlation matrix.
- Parameters:
-
| num_entities | the number of entities |
Member Function Documentation
void AddEntity |
( |
int |
entity_id |
) |
[inline, inherited] |
Add an entity to the CorrelationMatrix by growing it to the requested size.
Note that you still have to correctly compute and set the entity's correlation values
- Parameters:
-
| entity_id | the numerical ID of the entity |
static float ComputeCorrelation |
( |
IRatings |
ratings, |
|
|
EntityType |
entity_type, |
|
|
IList< Pair< int, float >> |
entity_ratings, |
|
|
int |
j, |
|
|
float |
shrinkage | |
|
) |
| | [inline, static] |
Compute correlation between two entities for given ratings.
- Parameters:
-
| ratings | the rating data |
| entity_type | the entity type, either USER or ITEM |
| entity_ratings | ratings identifying the first entity |
| j | the ID of second entity |
| shrinkage | the shrinkage parameter, set to 0 for the standard Pearson correlation without shrinkage |
static float ComputeCorrelation |
( |
IRatings |
ratings, |
|
|
EntityType |
entity_type, |
|
|
int |
i, |
|
|
int |
j, |
|
|
float |
shrinkage | |
|
) |
| | [inline, static] |
Compute correlation between two entities for given ratings.
- Parameters:
-
| ratings | the rating data |
| entity_type | the entity type, either USER or ITEM |
| i | the ID of the first entity |
| j | the ID of the second entity |
| shrinkage | the shrinkage parameter, set to 0 for the standard Pearson correlation without shrinkage |
override void ComputeCorrelations |
( |
IRatings |
ratings, |
|
|
EntityType |
entity_type | |
|
) |
| | [inline, virtual] |
Compute correlations for given ratings.
- Parameters:
-
| ratings | the rating data |
| entity_type | the entity type, either USER or ITEM |
Implements RatingCorrelationMatrix.
Creates a correlation matrix.
Gives out a useful warning if there is not enough memory
- Parameters:
-
| num_entities | the number of entities |
- Returns:
- the correlation matrix
Create a Pearson correlation matrix from given data.
- Parameters:
-
| ratings | the ratings data |
| entity_type | the entity type, either USER or ITEM |
| shrinkage | the shrinkage parameter, set to 0 for the standard Pearson correlation without shrinkage |
- Returns:
- the complete Pearson correlation matrix
int [] GetNearestNeighbors |
( |
int |
entity_id, |
|
|
uint |
k | |
|
) |
| | [inline, inherited] |
Get the k nearest neighbors of a given entity.
- Parameters:
-
| entity_id | the numerical ID of the entity |
| k | the neighborhood size |
- Returns:
- an array containing the numerical IDs of the k nearest neighbors
IList<int> GetPositivelyCorrelatedEntities |
( |
int |
entity_id |
) |
[inline, inherited] |
Get all entities that are positively correlated to an entity, sorted by correlation.
- Parameters:
-
- Returns:
- a sorted list of all entities that are positively correlated to entitiy_id
static CorrelationMatrix ReadCorrelationMatrix |
( |
StreamReader |
reader |
) |
[inline, static, inherited] |
Creates a CorrelationMatrix from the lines of a StreamReader.
In the first line, we expect to be the number of entities. All the other lines have the format
EntityID1 EntityID2 Correlation
where EntityID1 and EntityID2 are non-negative integers and Correlation is a floating point number.
- Parameters:
-
| reader | the StreamReader to read from |
double SumUp |
( |
int |
entity_id, |
|
|
ICollection< int > |
entities | |
|
) |
| | [inline, inherited] |
Sum up the correlations between a given entity and the entities in a collection.
- Parameters:
-
| entity_id | the numerical ID of the entity |
| entities | a collection containing the numerical IDs of the entities to compare to |
- Returns:
- the correlation sum
void Write |
( |
StreamWriter |
writer |
) |
[inline, inherited] |
Write out the correlations to a StreamWriter.
- Parameters:
-
Member Data Documentation
Number of entities, e.g. users or items.
Property Documentation
float Shrinkage [get, set] |
shrinkage parameter, if set to 0 we have the standard Pearson correlation without shrinkage
The documentation for this class was generated from the following file: