Github user felixcheung commented on a diff in the pull request:
https://github.com/apache/spark/pull/21710#discussion_r223573856
--- Diff: R/pkg/R/mllib_fpm.R ---
@@ -154,3 +160,74 @@ setMethod("write.ml", signature(object =
"FPGrowthModel", path = "character"),
function(object, path, overwrite = FALSE) {
write_internal(object, path, overwrite)
})
+
+#' PrefixSpan
+#'
+#' A parallel PrefixSpan algorithm to mine frequent sequential patterns.
+#' \code{spark.prefixSpan} returns an instance of PrefixSpan.
+#' \code{spark.findFrequentSequentialPatterns} returns a complete set of
frequent sequential
+#' patterns.
+#' For more details, see
+#'
\href{https://spark.apache.org/docs/latest/mllib-frequent-pattern-mining.html#prefixspan}{
+#' PrefixSpan}.
+#'
+#' @param minSupport Minimal support level.
+#' @param maxPatternLength Maximal pattern length.
+#' @param maxLocalProjDBSize Maximum number of items (including delimiters
used in the internal
+#' storage format) allowed in a projected
database before local
+#' processing.
+#' @param sequenceCol name of the sequence column in dataset.
+#' @param ... additional argument(s) passed to the method.
+#' @return \code{spark.prefixSpan} returns an instance of PrefixSpan
+#' @rdname spark.prefixSpan
+#' @name spark.prefixSpan
+#' @aliases spark.prefixSpan,ANY-method
+#' @examples
+#' \dontrun{
+#' df <- createDataFrame(list(list(list(list(1L, 2L), list(3L))),
+#' list(list(list(1L), list(3L, 2L), list(1L, 2L))),
+#' list(list(list(1L, 2L), list(5L))),
+#' list(list(list(6L)))), schema = c("sequence"))
+#' prefix_Span <- spark.prefixSpan(minSupport = 0.5, maxPatternLength = 5L,
+#' maxLocalProjDBSize = 32000000L)
+#' frequency <- spark.findFrequentSequentialPatterns(prefix_Span, df)
+#' showDF(frequency)
+#' }
+#' @note spark.prefixSpan since 3.0.0
+setMethod("spark.prefixSpan", signature(),
--- End diff --
sorry, I didn't see this before - an empty `signature()` is a bit usual
should we either
1) put one of these param as required (if they are required?) and its type
into the signature, eg. `signature(minSupport = "numeric")`
2) instead of having `spark.prefixSpan`, take all of these param into
`spark.findFrequentSequentialPatterns`
ie.
```
setMethod("spark.findFrequentSequentialPatterns",
signature(object = "PrefixSpan", data = "SparkDataFrame"),
function(object, data, minSupport = 0.1, maxPatternLength = 10L,
maxLocalProjDBSize = 32000000L, sequenceCol =
"sequence") {
```
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