[SPARK-10094] Pyspark ML Feature transformers marked as experimental

Modified class-level docstrings to mark all feature transformers in pyspark.ml as experimental.

Author: noelsmith <mail@noelsmith.com>

Closes #8623 from noel-smith/SPARK-10094-mark-pyspark-ml-trans-exp.

python/pyspark/ml/feature.py

@@ -36,6 +36,8 @@
 @inherit_doc
 class Binarizer(JavaTransformer, HasInputCol, HasOutputCol):
     """
+    .. note:: Experimental
+
     Binarize a column of continuous features given a threshold.
 
     >>> df = sqlContext.createDataFrame([(0.5,)], ["values"])
@@ -92,6 +94,8 @@ def getThreshold(self):
 @inherit_doc
 class Bucketizer(JavaTransformer, HasInputCol, HasOutputCol):
     """
+    .. note:: Experimental
+
     Maps a column of continuous features to a column of feature buckets.
 
     >>> df = sqlContext.createDataFrame([(0.1,), (0.4,), (1.2,), (1.5,)], ["values"])
@@ -169,6 +173,8 @@ def getSplits(self):
 @inherit_doc
 class DCT(JavaTransformer, HasInputCol, HasOutputCol):
     """
+    .. note:: Experimental
+
     A feature transformer that takes the 1D discrete cosine transform
     of a real vector. No zero padding is performed on the input vector.
     It returns a real vector of the same length representing the DCT.
@@ -232,6 +238,8 @@ def getInverse(self):
 @inherit_doc
 class ElementwiseProduct(JavaTransformer, HasInputCol, HasOutputCol):
     """
+    .. note:: Experimental
+
     Outputs the Hadamard product (i.e., the element-wise product) of each input vector
     with a provided "weight" vector. In other words, it scales each column of the dataset
     by a scalar multiplier.
@@ -289,6 +297,8 @@ def getScalingVec(self):
 @inherit_doc
 class HashingTF(JavaTransformer, HasInputCol, HasOutputCol, HasNumFeatures):
     """
+    .. note:: Experimental
+
     Maps a sequence of terms to their term frequencies using the
     hashing trick.
 
@@ -327,6 +337,8 @@ def setParams(self, numFeatures=1 << 18, inputCol=None, outputCol=None):
 @inherit_doc
 class IDF(JavaEstimator, HasInputCol, HasOutputCol):
     """
+    .. note:: Experimental
+
     Compute the Inverse Document Frequency (IDF) given a collection of documents.
 
     >>> from pyspark.mllib.linalg import DenseVector
@@ -387,6 +399,8 @@ def _create_model(self, java_model):
 
 class IDFModel(JavaModel):
     """
+    .. note:: Experimental
+
     Model fitted by IDF.
     """
 
@@ -395,6 +409,8 @@ class IDFModel(JavaModel):
 @ignore_unicode_prefix
 class NGram(JavaTransformer, HasInputCol, HasOutputCol):
     """
+    .. note:: Experimental
+
     A feature transformer that converts the input array of strings into an array of n-grams. Null
     values in the input array are ignored.
     It returns an array of n-grams where each n-gram is represented by a space-separated string of
@@ -463,6 +479,8 @@ def getN(self):
 @inherit_doc
 class Normalizer(JavaTransformer, HasInputCol, HasOutputCol):
     """
+    .. note:: Experimental
+
      Normalize a vector to have unit norm using the given p-norm.
 
     >>> from pyspark.mllib.linalg import Vectors
@@ -519,6 +537,8 @@ def getP(self):
 @inherit_doc
 class OneHotEncoder(JavaTransformer, HasInputCol, HasOutputCol):
     """
+    .. note:: Experimental
+
     A one-hot encoder that maps a column of category indices to a
     column of binary vectors, with at most a single one-value per row
     that indicates the input category index.
@@ -591,6 +611,8 @@ def getDropLast(self):
 @inherit_doc
 class PolynomialExpansion(JavaTransformer, HasInputCol, HasOutputCol):
     """
+    .. note:: Experimental
+
     Perform feature expansion in a polynomial space. As said in wikipedia of Polynomial Expansion,
     which is available at `http://en.wikipedia.org/wiki/Polynomial_expansion`, "In mathematics, an
     expansion of a product of sums expresses it as a sum of products by using the fact that
@@ -649,6 +671,8 @@ def getDegree(self):
 @ignore_unicode_prefix
 class RegexTokenizer(JavaTransformer, HasInputCol, HasOutputCol):
     """
+    .. note:: Experimental
+
     A regex based tokenizer that extracts tokens either by using the
     provided regex pattern (in Java dialect) to split the text
     (default) or repeatedly matching the regex (if gaps is false).
@@ -746,6 +770,8 @@ def getPattern(self):
 @inherit_doc
 class SQLTransformer(JavaTransformer):
     """
+    .. note:: Experimental
+
     Implements the transforms which are defined by SQL statement.
     Currently we only support SQL syntax like 'SELECT ... FROM __THIS__'
     where '__THIS__' represents the underlying table of the input dataset.
@@ -797,6 +823,8 @@ def getStatement(self):
 @inherit_doc
 class StandardScaler(JavaEstimator, HasInputCol, HasOutputCol):
     """
+    .. note:: Experimental
+
     Standardizes features by removing the mean and scaling to unit variance using column summary
     statistics on the samples in the training set.
 
@@ -870,6 +898,8 @@ def _create_model(self, java_model):
 
 class StandardScalerModel(JavaModel):
     """
+    .. note:: Experimental
+
     Model fitted by StandardScaler.
     """
 
@@ -891,6 +921,8 @@ def mean(self):
 @inherit_doc
 class StringIndexer(JavaEstimator, HasInputCol, HasOutputCol):
     """
+    .. note:: Experimental
+
     A label indexer that maps a string column of labels to an ML column of label indices.
     If the input column is numeric, we cast it to string and index the string values.
     The indices are in [0, numLabels), ordered by label frequencies.
@@ -929,6 +961,8 @@ def _create_model(self, java_model):
 
 class StringIndexerModel(JavaModel):
     """
+    .. note:: Experimental
+
     Model fitted by StringIndexer.
     """
 
@@ -1006,6 +1040,8 @@ def getCaseSensitive(self):
 @ignore_unicode_prefix
 class Tokenizer(JavaTransformer, HasInputCol, HasOutputCol):
     """
+    .. note:: Experimental
+
     A tokenizer that converts the input string to lowercase and then
     splits it by white spaces.
 
@@ -1051,6 +1087,8 @@ def setParams(self, inputCol=None, outputCol=None):
 @inherit_doc
 class VectorAssembler(JavaTransformer, HasInputCols, HasOutputCol):
     """
+    .. note:: Experimental
+
     A feature transformer that merges multiple columns into a vector column.
 
     >>> df = sqlContext.createDataFrame([(1, 0, 3)], ["a", "b", "c"])
@@ -1087,6 +1125,8 @@ def setParams(self, inputCols=None, outputCol=None):
 @inherit_doc
 class VectorIndexer(JavaEstimator, HasInputCol, HasOutputCol):
     """
+    .. note:: Experimental
+
     Class for indexing categorical feature columns in a dataset of [[Vector]].
 
     This has 2 usage modes:
@@ -1186,6 +1226,8 @@ def _create_model(self, java_model):
 
 class VectorIndexerModel(JavaModel):
     """
+    .. note:: Experimental
+
     Model fitted by VectorIndexer.
     """
 
@@ -1194,6 +1236,8 @@ class VectorIndexerModel(JavaModel):
 @ignore_unicode_prefix
 class Word2Vec(JavaEstimator, HasStepSize, HasMaxIter, HasSeed, HasInputCol, HasOutputCol):
     """
+    .. note:: Experimental
+
     Word2Vec trains a model of `Map(String, Vector)`, i.e. transforms a word into a code for further
     natural language processing or machine learning process.
 
@@ -1307,6 +1351,8 @@ def _create_model(self, java_model):
 
 class Word2VecModel(JavaModel):
     """
+    .. note:: Experimental
+
     Model fitted by Word2Vec.
     """
 
@@ -1332,6 +1378,8 @@ def findSynonyms(self, word, num):
 @inherit_doc
 class PCA(JavaEstimator, HasInputCol, HasOutputCol):
     """
+    .. note:: Experimental
+
     PCA trains a model to project vectors to a low-dimensional space using PCA.
 
     >>> from pyspark.mllib.linalg import Vectors
@@ -1387,6 +1435,8 @@ def _create_model(self, java_model):
 
 class PCAModel(JavaModel):
     """
+    .. note:: Experimental
+
     Model fitted by PCA.
     """
 
@@ -1470,6 +1520,8 @@ def _create_model(self, java_model):
 
 class RFormulaModel(JavaModel):
     """
+    .. note:: Experimental
+
     Model fitted by :py:class:`RFormula`.
     """