Github user mengxr commented on a diff in the pull request:
https://github.com/apache/spark/pull/7879#discussion_r36113315
--- Diff: python/pyspark/ml/feature.py ---
@@ -1110,6 +1110,80 @@ class PCAModel(JavaModel):
"""
+@inherit_doc
+class RFormula(JavaEstimator, HasFeaturesCol, HasLabelCol):
+ """
+ .. note:: Experimental
+
+ Implements the transforms required for fitting a dataset against an
+ R model formula. Currently we support a limited subset of the R
+ operators, including '~', '+', '-', and '.'. Also see the R formula
+ docs:
+ http://stat.ethz.ch/R-manual/R-patched/library/stats/html/formula.html
+
+ >>> df = sqlContext.createDataFrame([
+ ... (1.0, 1.0, "a"),
+ ... (0.0, 2.0, "b"),
+ ... (0.0, 0.0, "a")
+ ... ], ["y", "x", "s"])
+ >>> rf = RFormula(formula="y ~ x + s")
+ >>> rf.fit(df).transform(df).show()
--- End diff --
Yes, but I tried to create a small test case such that the behavior is
well-defined, e.g., the ordering of string values. If we use `a`, `b`, and `c`
with each appearing only once, how we determine the indices are not well
defined. Should be a TODO item, but not part of this PR.
For the test, it is following DataFrames tests. It might be simpler to read
as part of the documentation.
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