Transforms

Data wrangling and mapping from one schema to another.

Data wrangling

One of the key tools in DataVec is transformations. DataVec helps the user map a dataset from one schema to another, and provides a list of operations to convert types, format data, and convert a 2D dataset to sequence data.

Building a transform process

A transform process requires a Schema to successfully transform data. Both schema and transform process classes come with a helper Builder class which are useful for organizing code and avoiding complex constructors.

When both are combined together they look like the sample code below. Note how inputDataSchema is passed into the Builder constructor. Your transform process will fail to compile without it.

import org.datavec.api.transform.TransformProcess;

TransformProcess tp = new TransformProcess.Builder(inputDataSchema)
    .removeColumns("CustomerID","MerchantID")
    .filter(new ConditionFilter(new CategoricalColumnCondition("MerchantCountryCode", ConditionOp.NotInSet, new HashSet<>(Arrays.asList("USA","CAN")))))
    .conditionalReplaceValueTransform(
        "TransactionAmountUSD",     //Column to operate on
        new DoubleWritable(0.0),    //New value to use, when the condition is satisfied
        new DoubleColumnCondition("TransactionAmountUSD",ConditionOp.LessThan, 0.0)) //Condition: amount < 0.0
    .stringToTimeTransform("DateTimeString","YYYY-MM-DD HH:mm:ss.SSS", DateTimeZone.UTC)
    .renameColumn("DateTimeString", "DateTime")
    .transform(new DeriveColumnsFromTimeTransform.Builder("DateTime").addIntegerDerivedColumn("HourOfDay", DateTimeFieldType.hourOfDay()).build())
    .removeColumns("DateTime")
    .build();

Executing a transformation

Different "backends" for executors are available. Using the tp transform process above, here's how you can execute it locally using plain DataVec.

import org.datavec.local.transforms.LocalTransformExecutor;

List<List<Writable>> processedData = LocalTransformExecutor.execute(originalData, tp);

Debugging

Each operation in a transform process represents a "step" in schema changes. Sometimes, the resulting transformation is not the intended result. You can debug this by printing each step in the transform tp with the following:

//Now, print the schema after each time step:
int numActions = tp.getActionList().size();

for(int i=0; i<numActions; i++ ){
    System.out.println("\n\n==================================================");
    System.out.println("-- Schema after step " + i + " (" + tp.getActionList().get(i) + ") --");

    System.out.println(tp.getSchemaAfterStep(i));
}

Available transformations and conversions

TransformProcess

[source]

A TransformProcess defines an ordered list of transformations to be executed on some data

getFinalSchema

public Schema getFinalSchema()

Get the action list that this transform process will execute

return

getSchemaAfterStep

public Schema getSchemaAfterStep(int step)

Return the schema after executing all steps up to and including the specified step. Steps are indexed from 0: so getSchemaAfterStep(0) is after one transform has been executed.

param step Index of the step
return Schema of the data, after that (and all prior) steps have been executed

toJson

public String toJson()

Execute the full sequence of transformations for a single example. May return null if example is filtered NOTE: Some TransformProcess operations cannot be done on examples individually. Most notably, ConvertToSequence and ConvertFromSequence operations require the full data set to be processed at once

param input
return

toYaml

public String toYaml()

Convert the TransformProcess to a YAML string

return TransformProcess, as YAML

fromJson

public static TransformProcess fromJson(String json)

Deserialize a JSON String (created by {- link #toJson()}) to a TransformProcess

return TransformProcess, from JSON

fromYaml

public static TransformProcess fromYaml(String yaml)

Deserialize a JSON String (created by {- link #toJson()}) to a TransformProcess

return TransformProcess, from JSON

transform

public Builder transform(Transform transform)

Infer the categories for the given record reader for a particular column Note that each “column index” is a column in the context of: List record = ...; record.get(columnIndex);

Note that anything passed in as a column will be automatically converted to a string for categorical purposes.

The expected input is strings or numbers (which have sensible toString() representations)

Note that the returned categories will be sorted alphabetically

param recordReader the record reader to iterate through
param columnIndex te column index to get categories for
return

filter

public Builder filter(Filter filter)

Add a filter operation to be executed after the previously-added operations have been executed

param filter Filter operation to execute

filter

public Builder filter(Condition condition)

Add a filter operation, based on the specified condition.

If condition is satisfied (returns true): remove the example or sequence If condition is not satisfied (returns false): keep the example or sequence

param condition Condition to filter on

removeColumns

public Builder removeColumns(String... columnNames)

Remove all of the specified columns, by name

param columnNames Names of the columns to remove

removeColumns

public Builder removeColumns(Collection<String> columnNames)

Remove all of the specified columns, by name

param columnNames Names of the columns to remove

removeAllColumnsExceptFor

public Builder removeAllColumnsExceptFor(String... columnNames)

Remove all columns, except for those that are specified here

param columnNames Names of the columns to keep

removeAllColumnsExceptFor

public Builder removeAllColumnsExceptFor(Collection<String> columnNames)

Remove all columns, except for those that are specified here

param columnNames Names of the columns to keep

renameColumn

public Builder renameColumn(String oldName, String newName)

Rename a single column

param oldName Original column name
param newName New column name

renameColumns

public Builder renameColumns(List<String> oldNames, List<String> newNames)

Rename multiple columns

param oldNames List of original column names
param newNames List of new column names

reorderColumns

public Builder reorderColumns(String... newOrder)

Reorder the columns using a partial or complete new ordering. If only some of the column names are specified for the new order, the remaining columns will be placed at the end, according to their current relative ordering

param newOrder Names of the columns, in the order they will appear in the output

duplicateColumn

public Builder duplicateColumn(String column, String newName)

Duplicate a single column

param column Name of the column to duplicate
param newName Name of the new (duplicate) column

duplicateColumns

public Builder duplicateColumns(List<String> columnNames, List<String> newNames)

Duplicate a set of columns

param columnNames Names of the columns to duplicate
param newNames Names of the new (duplicated) columns

integerMathOp

public Builder integerMathOp(String column, MathOp mathOp, int scalar)

Perform a mathematical operation (add, subtract, scalar max etc) on the specified integer column, with a scalar

param column The integer column to perform the operation on
param mathOp The mathematical operation
param scalar The scalar value to use in the mathematical operation

integerColumnsMathOp

public Builder integerColumnsMathOp(String newColumnName, MathOp mathOp, String... columnNames)

Calculate and add a new integer column by performing a mathematical operation on a number of existing columns. New column is added to the end.

param newColumnName Name of the new/derived column
param mathOp Mathematical operation to execute on the columns
param columnNames Names of the columns to use in the mathematical operation

longMathOp

public Builder longMathOp(String columnName, MathOp mathOp, long scalar)

Perform a mathematical operation (add, subtract, scalar max etc) on the specified long column, with a scalar

param columnName The long column to perform the operation on
param mathOp The mathematical operation
param scalar The scalar value to use in the mathematical operation

longColumnsMathOp

public Builder longColumnsMathOp(String newColumnName, MathOp mathOp, String... columnNames)

Calculate and add a new long column by performing a mathematical operation on a number of existing columns. New column is added to the end.

param newColumnName Name of the new/derived column
param mathOp Mathematical operation to execute on the columns
param columnNames Names of the columns to use in the mathematical operation

floatMathOp

public Builder floatMathOp(String columnName, MathOp mathOp, float scalar)

Perform a mathematical operation (add, subtract, scalar max etc) on the specified double column, with a scalar

param columnName The float column to perform the operation on
param mathOp The mathematical operation
param scalar The scalar value to use in the mathematical operation

floatColumnsMathOp

public Builder floatColumnsMathOp(String newColumnName, MathOp mathOp, String... columnNames)

Calculate and add a new float column by performing a mathematical operation on a number of existing columns. New column is added to the end.

param newColumnName Name of the new/derived column
param mathOp Mathematical operation to execute on the columns
param columnNames Names of the columns to use in the mathematical operation

floatMathFunction

public Builder floatMathFunction(String columnName, MathFunction mathFunction)

Perform a mathematical operation (such as sin(x), ceil(x), exp(x) etc) on a column

param columnName Column name to operate on
param mathFunction MathFunction to apply to the column

doubleMathOp

public Builder doubleMathOp(String columnName, MathOp mathOp, double scalar)

Perform a mathematical operation (add, subtract, scalar max etc) on the specified double column, with a scalar

param columnName The double column to perform the operation on
param mathOp The mathematical operation
param scalar The scalar value to use in the mathematical operation

doubleColumnsMathOp

public Builder doubleColumnsMathOp(String newColumnName, MathOp mathOp, String... columnNames)

Calculate and add a new double column by performing a mathematical operation on a number of existing columns. New column is added to the end.

param newColumnName Name of the new/derived column
param mathOp Mathematical operation to execute on the columns
param columnNames Names of the columns to use in the mathematical operation

doubleMathFunction

public Builder doubleMathFunction(String columnName, MathFunction mathFunction)

Perform a mathematical operation (such as sin(x), ceil(x), exp(x) etc) on a column

param columnName Column name to operate on
param mathFunction MathFunction to apply to the column

timeMathOp

public Builder timeMathOp(String columnName, MathOp mathOp, long timeQuantity, TimeUnit timeUnit)

Perform a mathematical operation (add, subtract, scalar min/max only) on the specified time column

param columnName The integer column to perform the operation on
param mathOp The mathematical operation
param timeQuantity The quantity used in the mathematical op
param timeUnit The unit that timeQuantity is specified in

categoricalToOneHot

public Builder categoricalToOneHot(String... columnNames)

Convert the specified column(s) from a categorical representation to a one-hot representation. This involves the creation of multiple new columns each.

param columnNames Names of the categorical column(s) to convert to a one-hot representation

categoricalToInteger

public Builder categoricalToInteger(String... columnNames)

Convert the specified column(s) from a categorical representation to an integer representation. This will replace the specified categorical column(s) with an integer repreesentation, where each integer has the value 0 to numCategories-1.

param columnNames Name of the categorical column(s) to convert to an integer representation

integerToCategorical

public Builder integerToCategorical(String columnName, List<String> categoryStateNames)

Convert the specified column from an integer representation (assume values 0 to numCategories-1) to a categorical representation, given the specified state names

param columnName Name of the column to convert
param categoryStateNames Names of the states for the categorical column

integerToCategorical

public Builder integerToCategorical(String columnName, Map<Integer, String> categoryIndexNameMap)

Convert the specified column from an integer representation to a categorical representation, given the specified mapping between integer indexes and state names

param columnName Name of the column to convert
param categoryIndexNameMap Names of the states for the categorical column

integerToOneHot

public Builder integerToOneHot(String columnName, int minValue, int maxValue)

Convert an integer column to a set of 1 hot columns, based on the value in integer column

param columnName Name of the integer column
param minValue Minimum value possible for the integer column (inclusive)
param maxValue Maximum value possible for the integer column (inclusive)

addConstantColumn

public Builder addConstantColumn(String newColumnName, ColumnType newColumnType, Writable fixedValue)

Add a new column, where all values in the column are identical and as specified.

param newColumnName Name of the new column
param newColumnType Type of the new column
param fixedValue Value in the new column for all records

addConstantDoubleColumn

public Builder addConstantDoubleColumn(String newColumnName, double value)

Add a new double column, where the value for that column (for all records) are identical

param newColumnName Name of the new column
param value Value in the new column for all records

addConstantIntegerColumn

public Builder addConstantIntegerColumn(String newColumnName, int value)

Add a new integer column, where th e value for that column (for all records) are identical

param newColumnName Name of the new column
param value Value of the new column for all records

addConstantLongColumn

public Builder addConstantLongColumn(String newColumnName, long value)

Add a new integer column, where the value for that column (for all records) are identical

param newColumnName Name of the new column
param value Value in the new column for all records

convertToString

public Builder convertToString(String inputColumn)

Convert the specified column to a string.

param inputColumn the input column to convert
return builder pattern

convertToDouble

public Builder convertToDouble(String inputColumn)

Convert the specified column to a double.

param inputColumn the input column to convert
return builder pattern

convertToInteger

public Builder convertToInteger(String inputColumn)

Convert the specified column to an integer.

param inputColumn the input column to convert
return builder pattern

normalize

public Builder normalize(String column, Normalize type, DataAnalysis da)

Normalize the specified column with a given type of normalization

param column Column to normalize
param type Type of normalization to apply
param da DataAnalysis object

convertToSequence

public Builder convertToSequence(String keyColumn, SequenceComparator comparator)

Convert a set of independent records/examples into a sequence, according to some key. Within each sequence, values are ordered using the provided {- link SequenceComparator}

param keyColumn Column to use as a key (values with the same key will be combined into sequences)
param comparator A SequenceComparator to order the values within each sequence (for example, by time or String order)

convertToSequence

public Builder convertToSequence()

Convert a set of independent records/examples into a sequence; each example is simply treated as a sequence of length 1, without any join/group operations. Note that more commonly, joining/grouping is required; use {- link #convertToSequence(List, SequenceComparator)} for this functionality

convertToSequence

public Builder convertToSequence(List<String> keyColumns, SequenceComparator comparator)

Convert a set of independent records/examples into a sequence, where each sequence is grouped according to one or more key values (i.e., the values in one or more columns) Within each sequence, values are ordered using the provided {- link SequenceComparator}

param keyColumns Column to use as a key (values with the same key will be combined into sequences)
param comparator A SequenceComparator to order the values within each sequence (for example, by time or String order)

convertFromSequence

public Builder convertFromSequence()

Convert a sequence to a set of individual values (by treating each value in each sequence as a separate example)

splitSequence

public Builder splitSequence(SequenceSplit split)

Split sequences into 1 or more other sequences. Used for example to split large sequences into a set of smaller sequences

param split SequenceSplit that defines how splits will occur

trimSequence

public Builder trimSequence(int numStepsToTrim, boolean trimFromStart)

SequenceTrimTranform removes the first or last N values in a sequence. Note that the resulting sequence may be of length 0, if the input sequence is less than or equal to N.

param numStepsToTrim Number of time steps to trim from the sequence
param trimFromStart If true: Trim values from the start of the sequence. If false: trim values from the end.

offsetSequence

public Builder offsetSequence(List<String> columnsToOffset, int offsetAmount,
                                      SequenceOffsetTransform.OperationType operationType)

Perform a sequence of operation on the specified columns. Note that this also truncates sequences by the specified offset amount by default. Use {- code transform(new SequenceOffsetTransform(…)} to change this. See {- link SequenceOffsetTransform} for details on exactly what this operation does and how.

param columnsToOffset Columns to offset
param offsetAmount Amount to offset the specified columns by (positive offset: ‘columnsToOffset’ are moved to later time steps)
param operationType Whether the offset should be done in-place or by adding a new column

reduce

public Builder reduce(IAssociativeReducer reducer)

Reduce (i.e., aggregate/combine) a set of examples (typically by key). Note: In the current implementation, reduction operations can be performed only on standard (i.e., non-sequence) data

param reducer Reducer to use

reduceSequence

public Builder reduceSequence(IAssociativeReducer reducer)

Reduce (i.e., aggregate/combine) a set of sequence examples - for each sequence individually. Note: This method results in non-sequence data. If you would instead prefer sequences of length 1 after the reduction, use {- code transform(new ReduceSequenceTransform(reducer))}.

param reducer Reducer to use to reduce each window

reduceSequenceByWindow

public Builder reduceSequenceByWindow(IAssociativeReducer reducer, WindowFunction windowFunction)

Reduce (i.e., aggregate/combine) a set of sequence examples - for each sequence individually - using a window function. For example, take all records/examples in each 24-hour period (i.e., using window function), and convert them into a singe value (using the reducer). In this example, the output is a sequence, with time period of 24 hours.

param reducer Reducer to use to reduce each window
param windowFunction Window function to find apply on each sequence individually

sequenceMovingWindowReduce

public Builder sequenceMovingWindowReduce(String columnName, int lookback, ReduceOp op)

SequenceMovingWindowReduceTransform: Adds a new column, where the value is derived by: (a) using a window of the last N values in a single column, (b) Apply a reduction op on the window to calculate a new value for example, this transformer can be used to implement a simple moving average of the last N values, or determine the minimum or maximum values in the last N time steps.

For example, for a simple moving average, length 20: {- code new SequenceMovingWindowReduceTransform(“myCol”, 20, ReduceOp.Mean)}

param columnName Column name to perform windowing on
param lookback Look back period for windowing
param op Reduction operation to perform on each window

calculateSortedRank

public Builder calculateSortedRank(String newColumnName, String sortOnColumn, WritableComparator comparator)

CalculateSortedRank: calculate the rank of each example, after sorting example. For example, we might have some numerical “score” column, and we want to know for the rank (sort order) for each example, according to that column. The rank of each example (after sorting) will be added in a new Long column. Indexing is done from 0; examples will have values 0 to dataSetSize-1.

Currently, CalculateSortedRank can only be applied on standard (i.e., non-sequence) data Furthermore, the current implementation can only sort on one column

param newColumnName Name of the new column (will contain the rank for each example)
param sortOnColumn Column to sort on
param comparator Comparator used to sort examples

calculateSortedRank

public Builder calculateSortedRank(String newColumnName, String sortOnColumn, WritableComparator comparator,
                                           boolean ascending)

Currently, CalculateSortedRank can only be applied on standard (i.e., non-sequence) data Furthermore, the current implementation can only sort on one column

param newColumnName Name of the new column (will contain the rank for each example)
param sortOnColumn Column to sort on
param comparator Comparator used to sort examples
param ascending If true: sort ascending. False: descending

stringToCategorical

public Builder stringToCategorical(String columnName, List<String> stateNames)

Convert the specified String column to a categorical column. The state names must be provided.

param columnName Name of the String column to convert to categorical
param stateNames State names of the category

stringRemoveWhitespaceTransform

public Builder stringRemoveWhitespaceTransform(String columnName)

Remove all whitespace characters from the values in the specified String column

param columnName Name of the column to remove whitespace from

stringMapTransform

public Builder stringMapTransform(String columnName, Map<String, String> mapping)

Replace one or more String values in the specified column with new values.

Keys in the map are the original values; the Values in the map are their replacements. If a String appears in the data but does not appear in the provided map (as a key), that String values will not be modified.

param columnName Name of the column in which to do replacement
param mapping Map of oldValues -> newValues

stringToTimeTransform

public Builder stringToTimeTransform(String column, String format, DateTimeZone dateTimeZone)

Convert a String column (containing a date/time String) to a time column (by parsing the date/time String)

param column String column containing the date/time Strings
param format Format of the strings. Time format is specified as per http://www.joda.org/joda-time/apidocs/org/joda/time/format/DateTimeFormat.html
param dateTimeZone Timezone of the column

stringToTimeTransform

public Builder stringToTimeTransform(String column, String format, DateTimeZone dateTimeZone, Locale locale)

Convert a String column (containing a date/time String) to a time column (by parsing the date/time String)

param column String column containing the date/time Strings
param format Format of the strings. Time format is specified as per http://www.joda.org/joda-time/apidocs/org/joda/time/format/DateTimeFormat.html
param dateTimeZone Timezone of the column
param locale Locale of the column

appendStringColumnTransform

public Builder appendStringColumnTransform(String column, String toAppend)

Append a String to a specified column

param column Column to append the value to
param toAppend String to append to the end of each writable

conditionalReplaceValueTransform

public Builder conditionalReplaceValueTransform(String column, Writable newValue, Condition condition)

Replace the values in a specified column with a specified new value, if some condition holds. If the condition does not hold, the original values are not modified.

param column Column to operate on
param newValue Value to use as replacement, if condition is satisfied
param condition Condition that must be satisfied for replacement

conditionalReplaceValueTransformWithDefault

public Builder conditionalReplaceValueTransformWithDefault(String column, Writable yesVal, Writable noVal, Condition condition)

Replace the values in a specified column with a specified “yes” value, if some condition holds. Replace it with a “no” value, otherwise.

param column Column to operate on
param yesVal Value to use as replacement, if condition is satisfied
param noVal Value to use as replacement, if condition is not satisfied
param condition Condition that must be satisfied for replacement

conditionalCopyValueTransform

public Builder conditionalCopyValueTransform(String columnToReplace, String sourceColumn, Condition condition)

Replace the value in a specified column with a new value taken from another column, if a condition is satisfied/true. Note that the condition can be any generic condition, including on other column(s), different to the column that will be modified if the condition is satisfied/true.

param columnToReplace Name of the column in which values will be replaced (if condition is satisfied)
param sourceColumn Name of the column from which the new values will be
param condition Condition to use

replaceStringTransform

public Builder replaceStringTransform(String columnName, Map<String, String> mapping)

Replace one or more String values in the specified column that match regular expressions.

Keys in the map are the regular expressions; the Values in the map are their String replacements. For example:

Original

Regex

Replacement

Result

Data_Vec

DataVec

B1C2T3

\\d

one

BoneConeTone

'&nbsp&nbsp4.25&nbsp'

^\\s+|\\s+$

'4.25'

param columnName Name of the column in which to do replacement
param mapping Map of old values or regular expression to new values

ndArrayScalarOpTransform

public Builder ndArrayScalarOpTransform(String columnName, MathOp op, double value)

Element-wise NDArray math operation (add, subtract, etc) on an NDArray column

param columnName Name of the NDArray column to perform the operation on
param op Operation to perform
param value Value for the operation

ndArrayColumnsMathOpTransform

public Builder ndArrayColumnsMathOpTransform(String newColumnName, MathOp mathOp, String... columnNames)

Perform an element wise mathematical operation (such as add, subtract, multiply) on NDArray columns. The existing columns are unchanged, a new NDArray column is added

param newColumnName Name of the new NDArray column
param mathOp Operation to perform
param columnNames Name of the columns used as input to the operation

ndArrayMathFunctionTransform

public Builder ndArrayMathFunctionTransform(String columnName, MathFunction mathFunction)

Apply an element wise mathematical function (sin, tanh, abs etc) to an NDArray column. This operation is performed in place.

param columnName Name of the column to perform the operation on
param mathFunction Mathematical function to apply

ndArrayDistanceTransform

public Builder ndArrayDistanceTransform(String newColumnName, Distance distance, String firstCol,
                                                String secondCol)

Calculate a distance (cosine similarity, Euclidean, Manhattan) on two equal-sized NDArray columns. This operation adds a new Double column (with the specified name) with the result.

param newColumnName Name of the new column (result) to add
param distance Distance to apply
param firstCol first column to use in the distance calculation
param secondCol second column to use in the distance calculation

firstDigitTransform

public Builder firstDigitTransform(String inputColumn, String outputColumn)

FirstDigitTransform converts a column to a categorical column, with values being the first digit of the number. For example, “3.1415” becomes “3” and “2.0” becomes “2”. Negative numbers ignore the sign: “-7.123” becomes “7”. Note that two {- link FirstDigitTransform.Mode}s are supported, which determines how non-numerical entries should be handled: EXCEPTION_ON_INVALID: output has 10 category values (“0”, …, “9”), and any non-numerical values result in an exception INCLUDE_OTHER_CATEGORY: output has 11 category values (“0”, …, “9”, “Other”), all non-numerical values are mapped to “Other” FirstDigitTransform is useful (combined with {- link CategoricalToOneHotTransform} and Reductions) to implement Benford’s law.

param inputColumn Input column name
param outputColumn Output column name. If same as input, input column is replaced

firstDigitTransform

public Builder firstDigitTransform(String inputColumn, String outputColumn, FirstDigitTransform.Mode mode)

param inputColumn Input column name
param outputColumn Output column name. If same as input, input column is replaced
param mode See {- link FirstDigitTransform.Mode}

build

public TransformProcess build()

Create the TransformProcess object

CategoricalToIntegerTransform

[source]

Created by Alex on 4/03/2016.

map

public Object map(Object input)

Transform an object in to another object

param input the record to transform
return the transformed writable

mapSequence

public Object mapSequence(Object sequence)

Transform a sequence

param sequence

outputColumnName

public String outputColumnName()

The output column name after the operation has been applied

return the output column name

columnName

public String columnName()

The output column names This will often be the same as the input

return the output column names

CategoricalToOneHotTransform

[source]

Created by Alex on 4/03/2016.

map

public Object map(Object input)

Transform an object in to another object

param input the record to transform
return the transformed writable

mapSequence

public Object mapSequence(Object sequence)

Transform a sequence

param sequence

outputColumnName

public String outputColumnName()

The output column name after the operation has been applied

return the output column name

columnName

public String columnName()

The output column names This will often be the same as the input

return the output column names

IntegerToCategoricalTransform

[source]

map

public Object map(Object input)

Transform an object in to another object

param input the record to transform
return the transformed writable

mapSequence

public Object mapSequence(Object sequence)

Transform a sequence

param sequence

PivotTransform

[source]

Pivot transform operates on two columns:

a categorical column that operates as a key, and
Another column that contains a value Essentially, Pivot transform takes keyvalue pairs and breaks them out into separate columns.

For example, with schema [col0, key, value, col3] and values with key in {a,b,c} Output schema is [col0, key[a], key[b], key[c], col3] and input (col0Val, b, x, col3Val) gets mapped to (col0Val, 0, x, 0, col3Val).

When expanding columns, a default value is used - for example 0 for numerical columns.

transform

public Schema transform(Schema inputSchema)

param keyColumnName Key column to expand
param valueColumnName Name of the column that contains the value

StringToCategoricalTransform

[source]

Convert a String column to a categorical column

map

public Object map(Object input)

Transform an object in to another object

param input the record to transform
return the transformed writable

mapSequence

public Object mapSequence(Object sequence)

Transform a sequence

param sequence

AddConstantColumnTransform

[source]

Add a new column, where the values in that column for all records are identical (according to the specified value)

DuplicateColumnsTransform

[source]

Duplicate one or more columns. The duplicated columns are placed immediately after the original columns

transform

public Schema transform(Schema inputSchema)

param columnsToDuplicate List of columns to duplicate
param newColumnNames List of names for the new (duplicate) columns

map

public Object map(Object input)

Transform an object in to another object

param input the record to transform
return the transformed writable

mapSequence

public Object mapSequence(Object sequence)

Transform a sequence

param sequence

outputColumnName

public String outputColumnName()

The output column name after the operation has been applied

return the output column name

columnName

public String columnName()

The output column names This will often be the same as the input

return the output column names

RemoveAllColumnsExceptForTransform

[source]

Transform that removes all columns except for those that are explicitly specified as ones to keep To specify only the columns

map

public Object map(Object input)

Transform an object in to another object

param input the record to transform
return the transformed writable

mapSequence

public Object mapSequence(Object sequence)

Transform a sequence

param sequence

outputColumnName

public String outputColumnName()

The output column name after the operation has been applied

return the output column name

columnName

public String columnName()

The output column names This will often be the same as the input

return the output column names

RemoveColumnsTransform

[source]

Remove the specified columns from the data. To specify only the columns to keep,

map

public Object map(Object input)

Transform an object in to another object

param input the record to transform
return the transformed writable

mapSequence

public Object mapSequence(Object sequence)

Transform a sequence

param sequence

outputColumnName

public String outputColumnName()

The output column name after the operation has been applied

return the output column name

columnName

public String columnName()

The output column names This will often be the same as the input

return the output column names

RenameColumnsTransform

[source]

Rename one or more columns

map

public Object map(Object input)

Transform an object in to another object

param input the record to transform
return the transformed writable

mapSequence

public Object mapSequence(Object sequence)

Transform a sequence

param sequence

outputColumnName

public String outputColumnName()

The output column name after the operation has been applied

return the output column name

columnName

public String columnName()

The output column names This will often be the same as the input

return the output column names

ReorderColumnsTransform

[source]

Rearrange the order of the columns. Note: A partial list of columns can be used here. Any columns that are not explicitly mentioned will be placed after those that are in the output, without changing their relative order.

transform

public Schema transform(Schema inputSchema)

param newOrder A partial or complete order of the columns in the output

map

public Object map(Object input)

Transform an object in to another object

param input the record to transform
return the transformed writable

mapSequence

public Object mapSequence(Object sequence)

Transform a sequence

param sequence

outputColumnName

public String outputColumnName()

The output column name after the operation has been applied

return the output column name

columnName

public String columnName()

The output column names This will often be the same as the input

return the output column names

ConditionalCopyValueTransform

[source]

Note: For sequences, this transform use the convention that each step in the sequence is passed to the condition, and replaced (or not) separately (i.e., Condition.condition(List) is used on each time step individually)

transform

public Schema transform(Schema inputSchema)

param columnToReplace Name of the column in which to replace the old value
param sourceColumn Name of the column to get the new value from
param condition Condition

map

public Object map(Object input)

Transform an object in to another object

param input the record to transform
return the transformed writable

mapSequence

public Object mapSequence(Object sequence)

Transform a sequence

param sequence

outputColumnName

public String outputColumnName()

The output column name after the operation has been applied

return the output column name

columnName

public String columnName()

The output column names This will often be the same as the input

return the output column names

ConditionalReplaceValueTransform

[source]

Replace the value in a specified column with a new value, if a condition is satisfied/true. Note that the condition can be any generic condition, including on other column(s), different to the column that will be modified if the condition is satisfied/true.

transform

public Schema transform(Schema inputSchema)

param columnToReplace Name of the column in which to replace the old value with ‘newValue’, if the condition holds
param newValue New value to use
param condition Condition

map

public Object map(Object input)

Transform an object in to another object

param input the record to transform
return the transformed writable

mapSequence

public Object mapSequence(Object sequence)

Transform a sequence

param sequence

outputColumnName

public String outputColumnName()

The output column name after the operation has been applied

return the output column name

columnName

public String columnName()

The output column names This will often be the same as the input

return the output column names

ConditionalReplaceValueTransformWithDefault

[source]

Replace the value in a specified column with a ‘yes’ value, if a condition is satisfied/true. Replace the value of this same column with a ‘no’ value otherwise. Note that the condition can be any generic condition, including on other column(s), different to the column that will be modified if the condition is satisfied/true.

ConvertToDouble

[source]

Convert any value to an Double

map

public DoubleWritable map(Writable writable)

param column Name of the column to convert to a Double column

DoubleColumnsMathOpTransform

[source]

Add a new double column, calculated from one or more other columns. A new column (with the specified name) is added as the final column of the output. No other columns are modified. For example, if newColumnName==”newCol”, mathOp==Add, and columns=={“col1”,”col2”}, then the output column with name “newCol” has value col1+col2.

map

public Object map(Object input)

Transform an object in to another object

param input the record to transform
return the transformed writable

mapSequence

public Object mapSequence(Object sequence)

Transform a sequence

param sequence

DoubleMathFunctionTransform

[source]

A simple transform to do common mathematical operations, such as sin(x), ceil(x), etc.

DoubleMathOpTransform

[source]

Double mathematical operation. This is an in-place operation of the double column value and a double scalar.

map

public Object map(Object input)

Transform an object in to another object

param input the record to transform
return the transformed writable

mapSequence

public Object mapSequence(Object sequence)

Transform a sequence

param sequence

Log2Normalizer

[source]

Normalize by taking scale log2((in-columnMin)/(mean-columnMin) + 1) Maps values in range (columnMin to infinity) to (0 to infinity) Most suitable for values with a geometric/negative exponential type distribution.

map

public Object map(Object input)

Transform an object in to another object

param input the record to transform
return the transformed writable

MinMaxNormalizer

[source]

Normalizer to map (min to max) -> (newMin-to newMax) linearly.

Mathematically: (newMax-newMin)/(max-min) (x-min) + newMin

map

public Object map(Object input)

Transform an object in to another object

param input the record to transform
return the transformed writable

StandardizeNormalizer

[source]

Normalize using (x-mean)/stdev. Also known as a standard score, standardization etc.

map

public Object map(Object input)

Transform an object in to another object

param input the record to transform
return the transformed writable

SubtractMeanNormalizer

[source]

Normalize by substracting the mean

map

public Object map(Object input)

Transform an object in to another object

param input the record to transform
return the transformed writable

ConvertToInteger

[source]

Convert any value to an Integer.

map

public IntWritable map(Writable writable)

param column Name of the column to convert to an integer

IntegerColumnsMathOpTransform

[source]

Add a new integer column, calculated from one or more other columns. A new column (with the specified name) is added as the final column of the output. No other columns are modified. For example, if newColumnName==”newCol”, mathOp==MathOp.Add, and columns=={“col1”,”col2”}, then the output column with name “newCol” has value col1+col2. NOTE: Division here is using if a decimal output value is required.

toString

public String toString()

param newColumnName Name of the new column (output column)
param mathOp Mathematical operation. Only Add/Subtract/Multiply/Divide/Modulus is allowed here
param columns Columns to use in the mathematical operation

map

public Object map(Object input)

Transform an object in to another object

param input the record to transform
return the transformed writable

mapSequence

public Object mapSequence(Object sequence)

Transform a sequence

param sequence

IntegerMathOpTransform

[source]

Integer mathematical operation. This is an in-place operation of the integer column value and an integer scalar.

map

public Object map(Object input)

Transform an object in to another object

param input the record to transform
return the transformed writable

IntegerToOneHotTransform

[source]

Convert an integer column to a set of one-hot columns.

map

public Object map(Object input)

Transform an object in to another object

param input the record to transform
return the transformed writable

mapSequence

public Object mapSequence(Object sequence)

Transform a sequence

param sequence

outputColumnName

public String outputColumnName()

The output column name after the operation has been applied

return the output column name

columnName

public String columnName()

The output column names This will often be the same as the input

return the output column names

ReplaceEmptyIntegerWithValueTransform

[source]

Replace an empty/missing integer with a certain value.

map

public Object map(Object input)

Transform an object in to another object

param input the record to transform
return the transformed writable

ReplaceInvalidWithIntegerTransform

[source]

Replace an invalid (non-integer) value in a column with a specified integer

map

public Object map(Object input)

Transform an object in to another object

param input the record to transform
return the transformed writable

LongColumnsMathOpTransform

[source]

Add a new long column, calculated from one or more other columns. A new column (with the specified name) is added as the final column of the output. No other columns are modified. For example, if newColumnName==”newCol”, mathOp==MathOp.Add, and columns=={“col1”,”col2”}, then the output column with name “newCol” has value col1+col2. if a decimal output value is required.

map

public Object map(Object input)

Transform an object in to another object

param input the record to transform
return the transformed writable

mapSequence

public Object mapSequence(Object sequence)

Transform a sequence

param sequence

LongMathOpTransform

[source]

Long mathematical operation. This is an in-place operation of the long column value and an long scalar.

map

public Object map(Object input)

Transform an object in to another object

param input the record to transform
return the transformed writable

TextToCharacterIndexTransform

[source]

Convert each text value in a sequence to a longer sequence of integer indices. For example, “abc” would be converted to [1, 2, 3]. Values in other columns will be duplicated.

TextToTermIndexSequenceTransform

[source]

Convert each text value in a sequence to a longer sequence of integer indices. For example, “zero one two” would be converted to [0, 1, 2]. Values in other columns will be duplicated.

SequenceDifferenceTransform

[source]

SequenceDifferenceTransform: for an input sequence, calculate the difference on one column. For each time t, calculate someColumn(t) - someColumn(t-s), where s >= 1 is the ‘lookback’ period. Note: at t=0 (i.e., the first step in a sequence; or more generally, for all times t < s), there is no previous value these time steps:

Default: output = someColumn(t) - someColumn(max(t-s, 0))
SpecifiedValue: output = someColumn(t) - someColumn(t-s) if t-s >= 0, or a custom Writable object (for example, a DoubleWritable(0) or NullWritable).

Note: this is an in-place operation: i.e., the values in each column are modified. If the original values are and apply the difference operation in-place on the copy.

outputColumnName

public String outputColumnName()

Create a SequenceDifferenceTransform with default lookback of 1, and using FirstStepMode.Default. Output column name is the same as the input column name.

param columnName Name of the column to perform the operation on.

columnName

public String columnName()

The output column names This will often be the same as the input

return the output column names

map

public Object map(Object input)

Transform an object in to another object

param input the record to transform
return the transformed writable

mapSequence

public Object mapSequence(Object sequence)

Transform a sequence

param sequence

SequenceMovingWindowReduceTransform

[source]

SequenceMovingWindowReduceTransform Adds a new column, where the value is derived by: (a) using a window of the last N values in a single column, (b) Apply a reduction op on the window to calculate a new value for example, this transformer can be used to implement a simple moving average of the last N values, or determine the minimum or maximum values in the last N time steps.

defaultOutputColumnName

public static String defaultOutputColumnName(String originalName, int lookback, ReduceOp op)

Enumeration to specify how each cases are handled: For example, for a look back period of 20, how should the first 19 output values be calculated? Default: Perform your former reduction as normal, with as many values are available SpecifiedValue: use the given/specified value instead of the actual output value. For example, you could assign values of 0 or NullWritable to positions 0 through 18 of the output.

map

public Object map(Object input)

Transform an object in to another object

param input the record to transform
return the transformed writable

mapSequence

public Object mapSequence(Object sequence)

Transform a sequence

param sequence

outputColumnName

public String outputColumnName()

The output column name after the operation has been applied

return the output column name

columnName

public String columnName()

The output column names This will often be the same as the input

return the output column names

SequenceOffsetTransform

[source]

Sequence offset transform takes a sequence, and shifts The values in one or more columns by a specified number of times steps. It has 2 modes of operation (OperationType enum), with respect to the columns it operates on: InPlace: operations may be performed in-place, modifying the values in the specified columns NewColumn: operations may produce new columns, with the original (source) columns remaining unmodified

Additionally, there are 2 modes for handling values outside the original sequence (EdgeHandling enum): TrimSequence: the entire sequence is trimmed (start or end) by a specified number of steps SpecifiedValue: for any values outside of the original sequence, they are given a specified value

Note 1: When specifying offsets, they are done as follows: Positive offsets: move the values in the specified columns to a later time. Earlier time steps are either be trimmed or Given specified values; the last values in these columns will be truncated/removed.

Note 2: Care must be taken when using TrimSequence: for example, if we chain multiple sequence offset transforms on the one dataset, we may end up trimming much more than we want. In this case, it may be better to use SpecifiedValue, at the end.

AppendStringColumnTransform

[source]

Append a String to the values in a single column

map

public Object map(Object input)

Transform an object in to another object

param input the record to transform
return the transformed writable

ChangeCaseStringTransform

[source]

Change case (to, e.g, all lower case) of String column.

ConcatenateStringColumns

[source]

Concatenate values of one or more String columns into a new String column. Retains the constituent String columns so user must remove those manually, if desired.

TODO: use new String Reduce functionality in DataVec?

transform

public Schema transform(Schema inputSchema)

param columnsToConcatenate A partial or complete order of the columns in the output

map

public Object map(Object input)

Transform an object in to another object

param input the record to transform
return the transformed writable

mapSequence

public Object mapSequence(Object sequence)

Transform a sequence

param sequence

outputColumnName

public String outputColumnName()

The output column name after the operation has been applied

return the output column name

columnName

public String columnName()

The output column names This will often be the same as the input

return the output column names

ConvertToString

[source]

Convert any value to a string.

map

public Text map(Writable writable)

Transform the writable in to a string

param writable the writable to transform
return the string form of this writable

map

public Object map(Object input)

Transform an object in to another object

param input the record to transform
return the transformed writable

MapAllStringsExceptListTransform

[source]

This method maps all String values, except those is the specified list, to a single String value

map

public Object map(Object input)

Transform an object in to another object

param input the record to transform
return the transformed writable

RemoveWhiteSpaceTransform

[source]

String transform that removes all whitespace charaters

map

public Object map(Object input)

Transform an object in to another object

param input the record to transform
return the transformed writable

ReplaceEmptyStringTransform

[source]

Replace empty String values with the specified String

map

public Object map(Object input)

Transform an object in to another object

param input the record to transform
return the transformed writable

ReplaceStringTransform

[source]

Replaces String values that match regular expressions.

map

public Text map(final Writable writable)

Constructs a new ReplaceStringTransform using the specified

param columnName Name of the column
param map Key: regular expression; Value: replacement value

StringListToCategoricalSetTransform

[source]

Convert a delimited String to a list of binary categorical columns. Suppose the possible String values were {“a”,”b”,”c”,”d”} and the String column value to be converted contained the String “a,c”, then the 4 output columns would have values [“true”,”false”,”true”,”false”]

transform

public Schema transform(Schema inputSchema)

param columnName The name of the column to convert
param newColumnNames The names of the new columns to create
param categoryTokens The possible tokens that may be present. Note this list must have the same length and order as the newColumnNames list
param delimiter The delimiter for the Strings to convert

map

public Object map(Object input)

Transform an object in to another object

param input the record to transform
return the transformed writable

mapSequence

public Object mapSequence(Object sequence)

Transform a sequence

param sequence

outputColumnName

public String outputColumnName()

The output column name after the operation has been applied

return the output column name

columnName

public String columnName()

The output column names This will often be the same as the input

return the output column names

StringListToCountsNDArrayTransform

[source]

Converts String column into a bag-of-words (BOW) represented as an NDArray of “counts.” Note that the original column is removed in the process

transform

public Schema transform(Schema inputSchema)

param columnName The name of the column to convert
param vocabulary The possible tokens that may be present.
param delimiter The delimiter for the Strings to convert
param ignoreUnknown Whether to ignore unknown tokens

map

public Object map(Object input)

Transform an object in to another object

param input the record to transform
return the transformed writable

mapSequence

public Object mapSequence(Object sequence)

Transform a sequence

param sequence

outputColumnName

public String outputColumnName()

The output column name after the operation has been applied

return the output column name

columnName

public String columnName()

The output column names This will often be the same as the input

return the output column names

StringListToIndicesNDArrayTransform

[source]

Converts String column into a sparse bag-of-words (BOW) represented as an NDArray of indices. Appropriate for embeddings or as efficient storage before being expanded into a dense array.

StringMapTransform

[source]

A simple String -> String map function.

map

public Text map(Writable writable)

param columnName Name of the column
param map Key: From. Value: To

map

public Object map(Object input)

Transform an object in to another object

param input the record to transform
return the transformed writable

DeriveColumnsFromTimeTransform

[source]

Create a number of new columns by deriving their values from a Time column. Can be used for example to create new columns with the year, month, day, hour, minute, second etc.

map

public Object map(Object input)

Transform an object in to another object

param input the record to transform
return the transformed writable

mapSequence

public Object mapSequence(Object sequence)

Transform a sequence

param sequence

toString

public String toString()

The output column name after the operation has been applied

return the output column name

StringToTimeTransform

[source]

Convert a String column to a time column by parsing the date/time String, using a JodaTime.

Time format is specified as per http://www.joda.org/joda-time/apidocs/org/joda/time/format/DateTimeFormat.html

getNewColumnMetaData

public ColumnMetaData getNewColumnMetaData(String newName, ColumnMetaData oldColumnType)

Instantiate this without a time format specified. If this constructor is used, this transform will be allowed to handle several common transforms as defined in the static formats array.

param columnName Name of the String column
param timeZone Timezone for time parsing

map

public Object map(Object input)

Transform an object in to another object

param input the record to transform
return the transformed writable

TimeMathOpTransform

[source]

Transform math op on a time column

Note: only the following MathOps are supported: Add, Subtract, ScalarMin, ScalarMax For ScalarMin/Max, the TimeUnit must be milliseconds - i.e., value must be in epoch millisecond format

map

public Object map(Object input)

Transform an object in to another object

param input the record to transform
return the transformed writable

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Last updated 4 years ago