频繁模式挖掘的关联规则 [英] Association rules with Frequent Pattern Mining

问题描述

我想使用以下代码 Spark-Scala 提取一组事务的关联规则:

I want to extract association rules for a set of transaction with following code Spark-Scala:

val fpg = new FPGrowth().setMinSupport(minSupport).setNumPartitions(10)
val model = fpg.run(transactions)
model.generateAssociationRules(minConfidence).collect()

然而，产品的数量超过 10K，因此提取所有组合的规则在计算上具有表现力，而且我不需要它们全部.所以我只想成对提取:

however the number of products are more than 10K so extracting the rules for all combination is computationally expressive and also I do not need them all. So I want to extract only pair wise:

Product 1 ==> Product 2
Product 1 ==> Product 3
Product 3 ==> Product 1

而且我不关心其他组合，例如:

and I do not care about other combination such as:

[Product 1] ==> [Product 2, Product 3]
[Product 3,Product 1] ==> Product 2

有没有办法做到这一点?

Is there any way to do that?

谢谢，阿米尔

推荐答案

假设您的交易或多或少是这样的:

Assuming your transactions look more or less like this:

val transactions = sc.parallelize(Seq(
  Array("a", "b", "e"),
  Array("c", "b", "e", "f"),
  Array("a", "b", "c"),
  Array("c", "e", "f"),
  Array("d", "e", "f")
))

您可以尝试手动生成频繁项集并直接应用AssociationRules:

you can try to generate frequent itemsets manually and apply AssociationRules directly:

import org.apache.spark.mllib.fpm.AssociationRules
import org.apache.spark.mllib.fpm.FPGrowth.FreqItemset

val freqItemsets = transactions
  .flatMap(xs => 
    (xs.combinations(1) ++ xs.combinations(2)).map(x => (x.toList, 1L))
  )
  .reduceByKey(_ + _)
  .map{case (xs, cnt) => new FreqItemset(xs.toArray, cnt)}

val ar = new AssociationRules()
  .setMinConfidence(0.8)

val results = ar.run(freqItemsets)

注意事项:

• 不幸的是，您必须手动处理支持过滤.可以通过在 freqItemsets
上应用过滤器来完成
• 你应该在 flatMap
之前考虑增加分区数量

• 如果 freqItemsets 太大而无法处理，您可以将 freqItemsets 分成几个步骤来模拟实际的 FP 增长:

• unfortunately you'll have to handle filtering by support manually. It can be done by applying filter on freqItemsets
• you should consider increasing number of partitions before flatMap

• if freqItemsets is to large to be handled you can split freqItemsets into few steps to mimic actual FP-growth:

1. 生成 1-patterns 并按支持过滤
2. 仅使用步骤 1 中的频繁模式生成 2-模式

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