SequenceDifferenceTransform (datavec-api 0.9.1 API)

java.lang.Object
- org.datavec.api.transform.transform.sequence.SequenceDifferenceTransform

All Implemented Interfaces:

Serializable, ColumnOp, Transform
```
public class SequenceDifferenceTransform
extends Object
implements Transform
```
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 from which to calculate the difference. The SequenceDifferenceTransform.FirstStepMode enumeration provides the following ways of handling these time steps:
1. Default: output = someColumn(t) - someColumn(max(t-s, 0)) 2. 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 to be retained in the data set, first make a copy (for example, using TransformProcess.Builder.duplicateColumn(String, String)) and apply the difference operation in-place on the copy.

Author:

Alex Black

See Also:

Serialized Form

Nested Class Summary

Nested Classes
Modifier and Type Class and Description

static class SequenceDifferenceTransform.FirstStepMode

Nested Classes
Modifier and Type	Class and Description
`static class`	`SequenceDifferenceTransform.FirstStepMode`

Constructor Summary

Constructors
Constructor and Description
`SequenceDifferenceTransform(String columnName)` Create a SequenceDifferenceTransform with default lookback of 1, and using FirstStepMode.Default.
`SequenceDifferenceTransform(String columnName, String newColumnName, int lookback)` Create a SequenceDifferenceTransform with default lookback of 1, and using FirstStepMode.Default, where the output column name is specified
`SequenceDifferenceTransform(String columnName, String newColumnName, int lookback, SequenceDifferenceTransform.FirstStepMode firstStepMode, Writable specifiedValueWritable)` Create a SequenceDifferenceTransform with default lookback of 1, and using FirstStepMode.Default, where the output column name is specified

Method Summary

All Methods Instance Methods Concrete Methods
Modifier and Type	Method and Description
`String`	`columnName()` Returns a singular column name this op is meant to run on
`String[]`	`columnNames()` Returns column names this op is meant to run on
`Schema`	`getInputSchema()` Getter for input schema
`List<Writable>`	`map(List<Writable> writables)` Transform a writable in to another writable
`Object`	`map(Object input)` Transform an object in to another object
`List<List<Writable>>`	`mapSequence(List<List<Writable>> sequence)` Transform a sequence
`Object`	`mapSequence(Object sequence)` Transform a sequence
`String`	`outputColumnName()` The output column name after the operation has been applied
`String[]`	`outputColumnNames()` The output column names This will often be the same as the input
`void`	`setInputSchema(Schema inputSchema)` Set the input schema.
`Schema`	`transform(Schema inputSchema)` Get the output schema for this transformation, given an input schema

Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

- Constructor Detail
  - SequenceDifferenceTransform
```
public SequenceDifferenceTransform(String columnName)
```
    Create a SequenceDifferenceTransform with default lookback of 1, and using FirstStepMode.Default. Output column name is the same as the input column name.
    
    Parameters:
    
    columnName - Name of the column to perform the operation on.
  - SequenceDifferenceTransform
```
public SequenceDifferenceTransform(String columnName,
                                   String newColumnName,
                                   int lookback)
```
    Create a SequenceDifferenceTransform with default lookback of 1, and using FirstStepMode.Default, where the output column name is specified
    
    Parameters:
    
    columnName - Name of the column to perform the operation on.
    
    newColumnName - New name for the column. May be same as the origina lcolumn name
    
    lookback - Lookback period, in number of time steps. Must be > 0
  - SequenceDifferenceTransform
```
public SequenceDifferenceTransform(String columnName,
                                   String newColumnName,
                                   int lookback,
                                   SequenceDifferenceTransform.FirstStepMode firstStepMode,
                                   Writable specifiedValueWritable)
```
    Create a SequenceDifferenceTransform with default lookback of 1, and using FirstStepMode.Default, where the output column name is specified
    
    Parameters:
    
    columnName - Name of the column to perform the operation on.
    
    newColumnName - New name for the column. May be same as the origina lcolumn name
    
    lookback - Lookback period, in number of time steps. Must be > 0
    
    firstStepMode - see SequenceDifferenceTransform.FirstStepMode
    
    specifiedValueWritable - Must be null if using FirstStepMode.Default, or non-null if using FirstStepMode.SpecifiedValue
- Method Detail
  - outputColumnName
```
public String outputColumnName()
```
    The output column name after the operation has been applied
    
    Specified by:
    
    outputColumnName in interface ColumnOp
    
    Returns:
    
    the output column name
  - outputColumnNames
```
public String[] outputColumnNames()
```
    The output column names This will often be the same as the input
    
    Specified by:
    
    outputColumnNames in interface ColumnOp
    
    Returns:
    
    the output column names
  - columnNames
```
public String[] columnNames()
```
    Returns column names this op is meant to run on
    
    Specified by:
    
    columnNames in interface ColumnOp
    
    Returns:
  - columnName
```
public String columnName()
```
    Returns a singular column name this op is meant to run on
    
    Specified by:
    
    columnName in interface ColumnOp
    
    Returns:
  - transform
```
public Schema transform(Schema inputSchema)
```
    Description copied from interface: ColumnOp
    
    Get the output schema for this transformation, given an input schema
    
    Specified by:
    
    transform in interface ColumnOp
  - setInputSchema
```
public void setInputSchema(Schema inputSchema)
```
    Description copied from interface: ColumnOp
    
    Set the input schema.
    
    Specified by:
    
    setInputSchema in interface ColumnOp
  - getInputSchema
```
public Schema getInputSchema()
```
    Description copied from interface: ColumnOp
    
    Getter for input schema
    
    Specified by:
    
    getInputSchema in interface ColumnOp
    
    Returns:
  - map
```
public List<Writable> map(List<Writable> writables)
```
    Description copied from interface: Transform
    
    Transform a writable in to another writable
    
    Specified by:
    
    map in interface Transform
    
    Parameters:
    
    writables - the record to transform
    
    Returns:
    
    the transformed writable
  - mapSequence
```
public List<List<Writable>> mapSequence(List<List<Writable>> sequence)
```
    Description copied from interface: Transform
    
    Transform a sequence
    
    Specified by:
    
    mapSequence in interface Transform
  - map
```
public Object map(Object input)
```
    Transform an object in to another object
    
    Specified by:
    
    map in interface Transform
    
    Parameters:
    
    input - the record to transform
    
    Returns:
    
    the transformed writable
  - mapSequence
```
public Object mapSequence(Object sequence)
```
    Transform a sequence
    
    Specified by:
    
    mapSequence in interface Transform
    
    Parameters:
    
    sequence -

Class SequenceDifferenceTransform

Nested Class Summary

Constructor Summary

Method Summary

Methods inherited from class java.lang.Object

Constructor Detail

SequenceDifferenceTransform

SequenceDifferenceTransform

SequenceDifferenceTransform

Method Detail

outputColumnName

outputColumnNames

columnNames

columnName

transform

setInputSchema

getInputSchema

map

mapSequence

map

mapSequence