org.apache.spark.ml.feature

Class OneHotEncoderEstimator

Object

org.apache.spark.ml.PipelineStage

org.apache.spark.ml.Estimator<OneHotEncoderModel>

org.apache.spark.ml.feature.OneHotEncoderEstimator

All Implemented Interfaces:

java.io.Serializable, Logging, Params, DefaultParamsWritable, Identifiable, MLWritable

public class OneHotEncoderEstimator
extends Estimator<OneHotEncoderModel>
implements DefaultParamsWritable

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. For example with 5 categories, an input value of 2.0 would map to an output vector of [0.0, 0.0, 1.0, 0.0]. The last category is not included by default (configurable via dropLast), because it makes the vector entries sum up to one, and hence linearly dependent. So an input value of 4.0 maps to [0.0, 0.0, 0.0, 0.0].

See Also:

StringIndexer for converting categorical values into category indices, Serialized Form

Note:

This is different from scikit-learn's OneHotEncoder, which keeps all categories. The output vectors are sparse.

When handleInvalid is configured to 'keep', an extra "category" indicating invalid values is added as last category. So when dropLast is true, invalid values are encoded as all-zeros vector.

, When encoding multi-column by using inputCols and outputCols params, input/output cols come in pairs, specified by the order in the arrays, and each pair is treated independently.

Constructor Summary

Constructors

Constructor and Description
OneHotEncoderEstimator()
OneHotEncoderEstimator(String uid)

Method Summary

Modifier and Type	Method and Description
static Params	clear(Param<?> param)
OneHotEncoderEstimator	copy(ParamMap extra) Creates a copy of this instance with the same UID and some extra params.
static BooleanParam	dropLast()
BooleanParam	dropLast() Whether to drop the last category in the encoded vector (default: true)
static String	explainParam(Param<?> param)
static String	explainParams()
static ParamMap	extractParamMap()
static ParamMap	extractParamMap(ParamMap extra)
OneHotEncoderModel	fit(Dataset<?> dataset) Fits a model to the input data.
static <T> scala.Option<T>	get(Param<T> param)
static <T> scala.Option<T>	getDefault(Param<T> param)
static boolean	getDropLast()
boolean	getDropLast()
static String	getHandleInvalid()
static String[]	getInputCols()
static <T> T	getOrDefault(Param<T> param)
static String[]	getOutputCols()
static Param<Object>	getParam(String paramName)
static Param<String>	handleInvalid()
Param<String>	handleInvalid() Param for how to handle invalid data during transform().
static <T> boolean	hasDefault(Param<T> param)
static boolean	hasParam(String paramName)
static StringArrayParam	inputCols()
static boolean	isDefined(Param<?> param)
static boolean	isSet(Param<?> param)
static OneHotEncoderEstimator	load(String path)
static StringArrayParam	outputCols()
static Param<?>[]	params()
static void	save(String path)
static <T> Params	set(Param<T> param, T value)
OneHotEncoderEstimator	setDropLast(boolean value)
OneHotEncoderEstimator	setHandleInvalid(String value)
OneHotEncoderEstimator	setInputCols(String[] values)
OneHotEncoderEstimator	setOutputCols(String[] values)
static String	toString()
StructType	transformSchema(StructType schema) :: DeveloperApi ::
String	uid() An immutable unique ID for the object and its derivatives.
StructType	validateAndTransformSchema(StructType schema, boolean dropLast, boolean keepInvalid)
static MLWriter	write()

Methods inherited from class org.apache.spark.ml.Estimator

fit, fit, fit, fit

Methods inherited from class Object

equals, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Methods inherited from interface org.apache.spark.ml.param.shared.HasHandleInvalid

getHandleInvalid

Methods inherited from interface org.apache.spark.ml.param.shared.HasInputCols

getInputCols, inputCols

Methods inherited from interface org.apache.spark.ml.param.shared.HasOutputCols

getOutputCols, outputCols

Methods inherited from interface org.apache.spark.ml.param.Params

clear, copyValues, defaultCopy, defaultParamMap, explainParam, explainParams, extractParamMap, extractParamMap, get, getDefault, getOrDefault, getParam, hasDefault, hasParam, isDefined, isSet, paramMap, params, set, set, set, setDefault, setDefault, shouldOwn

Methods inherited from interface org.apache.spark.ml.util.Identifiable

toString

Methods inherited from interface org.apache.spark.ml.util.DefaultParamsWritable

write

Methods inherited from interface org.apache.spark.ml.util.MLWritable

save

Methods inherited from interface org.apache.spark.internal.Logging

initializeLogging, initializeLogIfNecessary, initializeLogIfNecessary, isTraceEnabled, log_, log, logDebug, logDebug, logError, logError, logInfo, logInfo, logName, logTrace, logTrace, logWarning, logWarning

Constructor Detail

OneHotEncoderEstimator

public OneHotEncoderEstimator(String uid)

OneHotEncoderEstimator

public OneHotEncoderEstimator()

Method Detail

load

public static OneHotEncoderEstimator load(String path)

toString

public static String toString()

params

public static Param<?>[] params()

explainParam

public static String explainParam(Param<?> param)

explainParams

public static String explainParams()

isSet

public static final boolean isSet(Param<?> param)

isDefined

public static final boolean isDefined(Param<?> param)

hasParam

public static boolean hasParam(String paramName)

getParam

public static Param<Object> getParam(String paramName)

set

public static final <T> Params set(Param<T> param,
                                   T value)

get

public static final <T> scala.Option<T> get(Param<T> param)

clear

public static final Params clear(Param<?> param)

getOrDefault

public static final <T> T getOrDefault(Param<T> param)

getDefault

public static final <T> scala.Option<T> getDefault(Param<T> param)

hasDefault

public static final <T> boolean hasDefault(Param<T> param)

extractParamMap

public static final ParamMap extractParamMap(ParamMap extra)

extractParamMap

public static final ParamMap extractParamMap()

getHandleInvalid

public static final String getHandleInvalid()

inputCols

public static final StringArrayParam inputCols()

getInputCols

public static final String[] getInputCols()

outputCols

public static final StringArrayParam outputCols()

getOutputCols

public static final String[] getOutputCols()

handleInvalid

public static Param<String> handleInvalid()

dropLast

public static final BooleanParam dropLast()

getDropLast

public static boolean getDropLast()

save

public static void save(String path)
                 throws java.io.IOException

Throws:

java.io.IOException

write

public static MLWriter write()

uid

public String uid()

Description copied from interface: Identifiable

An immutable unique ID for the object and its derivatives.

Specified by:

uid in interface Identifiable

Returns:

(undocumented)

setInputCols

public OneHotEncoderEstimator setInputCols(String[] values)

setOutputCols

public OneHotEncoderEstimator setOutputCols(String[] values)

setDropLast

public OneHotEncoderEstimator setDropLast(boolean value)

setHandleInvalid

public OneHotEncoderEstimator setHandleInvalid(String value)

transformSchema

public StructType transformSchema(StructType schema)

Description copied from class: PipelineStage

:: DeveloperApi ::

Check transform validity and derive the output schema from the input schema.

We check validity for interactions between parameters during transformSchema and raise an exception if any parameter value is invalid. Parameter value checks which do not depend on other parameters are handled by Param.validate().

Typical implementation should first conduct verification on schema change and parameter validity, including complex parameter interaction checks.

Specified by:

transformSchema in class PipelineStage

Parameters:

schema - (undocumented)

Returns:

(undocumented)

fit

public OneHotEncoderModel fit(Dataset<?> dataset)

Description copied from class: Estimator

Fits a model to the input data.

Specified by:

fit in class Estimator<OneHotEncoderModel>

Parameters:

dataset - (undocumented)

Returns:

(undocumented)

copy

public OneHotEncoderEstimator copy(ParamMap extra)

Description copied from interface: Params

Creates a copy of this instance with the same UID and some extra params. Subclasses should implement this method and set the return type properly. See defaultCopy().

Specified by:

copy in interface Params

Specified by:

copy in class Estimator<OneHotEncoderModel>

Parameters:

extra - (undocumented)

Returns:

(undocumented)

handleInvalid

public Param<String> handleInvalid()

Param for how to handle invalid data during transform(). Options are 'keep' (invalid data presented as an extra categorical feature) or 'error' (throw an error). Note that this Param is only used during transform; during fitting, invalid data will result in an error. Default: "error"

Specified by:

handleInvalid in interface HasHandleInvalid

Returns:

(undocumented)

dropLast

public BooleanParam dropLast()

Whether to drop the last category in the encoded vector (default: true)

Returns:

(undocumented)

getDropLast

public boolean getDropLast()

validateAndTransformSchema

public StructType validateAndTransformSchema(StructType schema,
                                             boolean dropLast,
                                             boolean keepInvalid)