ml_prefixspan

Frequent Pattern Mining – PrefixSpan

Description

PrefixSpan algorithm for mining frequent itemsets.

Usage

ml_prefixspan(
  x,
  seq_col = "sequence",
  min_support = 0.1,
  max_pattern_length = 10,
  max_local_proj_db_size = 3.2e+07,
  uid = random_string("prefixspan_"),
  ...
)

ml_freq_seq_patterns(model)

Arguments

Argument Description
x A spark_connection, ml_pipeline, or a tbl_spark.
seq_col The name of the sequence column in dataset (default “sequence”). Rows with nulls in this column are ignored.
min_support The minimum support required to be considered a frequent sequential pattern.
max_pattern_length The maximum length of a frequent sequential pattern. Any frequent pattern exceeding this length will not be included in the results.
max_local_proj_db_size The maximum number of items allowed in a prefix-projected database before local iterative processing of the projected database begins. This parameter should be tuned with respect to the size of your executors.
uid A character string used to uniquely identify the ML estimator.
Optional arguments; currently unused.
model A Prefix Span model.

Examples


library(sparklyr)
sc <- spark_connect(master = "local", version = "2.4.0")

items_df <- tibble::tibble(
  seq = list(
    list(list(1, 2), list(3)),
    list(list(1), list(3, 2), list(1, 2)),
    list(list(1, 2), list(5)),
    list(list(6))
  )
)
items_sdf <- copy_to(sc, items_df, overwrite = TRUE)

prefix_span_model <- ml_prefixspan(
  sc,
  seq_col = "seq",
  min_support = 0.5,
  max_pattern_length = 5,
  max_local_proj_db_size = 32000000
)

frequent_items <- prefix_span_model$frequent_sequential_patterns(items_sdf) %>% collect()