Cassandra基于Mahout用户朋友推荐 [英] Cassandra based Mahout user friend recommendations
问题描述
我要推荐一个用户,当前用户可以添加为朋友的用户列表。
I want to recommend a user , a list of users which the current user can add as friends.
我使用Cassandra和mahout。已经有 CassandraDataModel 在mahout集成包中。我想使用这个类。
I am using Cassandra and mahout. there is already a implementation of CassandraDataModel in mahout integration package. I want to use this class.
所以我的推荐类如下所示
So my recommend-er class looks like follows
public class UserFriendsRecommender {
@Inject
private CassandraDataModel dataModel;
public List<RecommendedItem> recommend(Long userId, int number) throws TasteException{
UserSimilarity userSimilarity = new PearsonCorrelationSimilarity(dataModel);
// Optional:
userSimilarity.setPreferenceInferrer(new AveragingPreferenceInferrer(dataModel));
UserNeighborhood neighborhood =
new NearestNUserNeighborhood(3, userSimilarity, dataModel);
Recommender recommender = new GenericUserBasedRecommender(dataModel, neighborhood, userSimilarity);
Recommender cachingRecommender = new CachingRecommender(recommender);
List<RecommendedItem> recommendations = cachingRecommender.recommend(userId, number);
return recommendations;
}
}
CassandraDataModel有4列的家族
CassandraDataModel has 4 column familys
static final String USERS_CF = "users";
static final String ITEMS_CF = "items";
static final String USER_IDS_CF = "userIDs";
static final String ITEM_IDS_CF = "itemIDs";
我很难理解这个类,特别是列族。是有任何例子,我可以寻找或如果有人可以解释将是一个很好的例子。
i have a hard time understanding this class especially the column family's. is there any example where i can look for or if someone can explain will be great with a small example.?
javadoc说这个
javadoc says this
* <p>
* First, it uses a column family called "users". This is keyed by the user ID
* as an 8-byte long. It contains a column for every preference the user
* expresses. The column name is item ID, again as an 8-byte long, and value is
* a floating point value represnted as an IEEE 32-bit floating poitn value.
* </p>
*
* <p>
* It uses an analogous column family called "items" for the same data, but
* keyed by item ID rather than user ID. In this column family, column names are
* user IDs instead.
* </p>
*
* <p>
* It uses a column family called "userIDs" as well, with an identical schema.
* It has one row under key 0. It contains a column for every user ID in the
* model. It has no values.
* </p>
*
* <p>
* Finally it also uses an analogous column family "itemIDs" containing item
* IDs.
* </p>
推荐答案
CassandraDataMdoel需要的列族的所有以下说明
All the following instructions about required column families by CassandraDataMdoel should be performed in cassandra-cli under the keyspace you created (recommender or other name).
1:表用户
userID是行键,每个itemID都有一个单独的列名,值是首选项:
userID is the row key, each itemID has a separate column name, and value is the preference:
CREATE COLUMN FAMILY users
WITH comparator = LongType
AND key_validation_class=LongType
AND default_validation_class=FloatType;
插入值:
set users[0][0]='1.0';
set users[1][0]='3.0';
set users[2][2]='1.0';
2:表格项
CREATE COLUMN FAMILY items
WITH comparator = LongType
AND key_validation_class=LongType
AND default_validation_class=FloatType;
插入值:
set items[0][0]='1.0';
set items[0][1]='3.0';
set items[2][2]='1.0';
3:表userIDs
3: Table userIDs
只有一行,但有许多列,即每个userID都有一个单独的列:
This table just has one row, but many columns, i.e. each userID has a separate column:
CREATE COLUMN FAMILY userIDs
WITH comparator = LongType
AND key_validation_class=LongType;
插入值:
set userIDs[0][0]='';
set userIDs[0][1]='';
set userIDs[0][2]='';
4:表itemID:
4: Table itemIDs:
表只有一行,但有很多列,即每个itemID都有一个单独的列:
This table just has one row, but many columns, i.e. each itemID has a separate column:
CREATE COLUMN FAMILY itemIDs
WITH comparator = LongType
AND key_validation_class=LongType;
插入值:
set itemIDs[0][0]='';
set itemIDs[0][1]='';
set itemIDs[0][2]='';
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