weka.core.converters
Interface Loader

All Superinterfaces:

java.io.Serializable

All Known Implementing Classes:

AbstractLoader

public interface Loader

extends java.io.Serializable

Interface to something that can load Instances from an input source in some format.

Version:

$Revision: 1.6 $

Author:

Mark Hall (mhall@cs.waikato.ac.nz)

Method Summary

Instances	getDataSet() Return the full data set.
Instance	getNextInstance() Read the data set incrementally---get the next instance in the data set or returns null if there are no more instances to get.
Instances	getStructure() Determines and returns (if possible) the structure (internally the header) of the data set as an empty set of instances.
void	setSource(java.io.File file) Resets the Loader object and sets the source of the data set to be the supplied File object.
void	setSource(java.io.InputStream input) Resets the Loader object and sets the source of the data set to be the supplied InputStream.

Method Detail

setSource

public void setSource(java.io.File file)
               throws java.io.IOException

Resets the Loader object and sets the source of the data set to be the supplied File object.

Parameters:

file - the File

Throws:

java.io.IOException - if an error occurs support loading from a File.

    public_normal_behavior
      requires: file != null
                && (* file exists *);
      modifiable: model_sourceSupplied, model_structureDetermined;
      ensures: model_sourceSupplied == true 
               && model_structureDetermined == false;
  also
    public_exceptional_behavior
      requires: file == null
                || (* file does not exist *);
    signals: (IOException);
 

setSource

public void setSource(java.io.InputStream input)
               throws java.io.IOException

Resets the Loader object and sets the source of the data set to be the supplied InputStream.

Parameters:

input - the source InputStream

Throws:

java.io.IOException - if this Loader doesn't support loading from a File.

getStructure

public Instances getStructure()
                       throws java.io.IOException

Determines and returns (if possible) the structure (internally the header) of the data set as an empty set of instances.

Returns:

the structure of the data set as an empty set of Instances

Throws:

java.io.IOException - if there is no source or parsing fails

    public_normal_behavior
      requires: model_sourceSupplied == true
                && model_structureDetermined == false
                && (* successful parse *);
      modifiable: model_structureDetermined;
      ensures: \result != null
               && \result.numInstances() == 0
               && model_structureDetermined == true;
  also
    public_exceptional_behavior
      requires: model_sourceSupplied == false
                || (* unsuccessful parse *);
      signals: (IOException);
 

getDataSet

public Instances getDataSet()
                     throws java.io.IOException

Return the full data set. If the structure hasn't yet been determined by a call to getStructure then the method should do so before processing the rest of the data set.

Returns:

the full data set as an Instances object

Throws:

java.io.IOException - if there is an error during parsing or if getNextInstance has been called on this source (either incremental or batch loading can be used, not both).

    public_normal_behavior
      requires: model_sourceSupplied == true
                && (* successful parse *);
      modifiable: model_structureDetermined;
      ensures: \result != null
               && \result.numInstances() >= 0
               && model_structureDetermined == true;
  also
    public_exceptional_behavior
      requires: model_sourceSupplied == false
                || (* unsuccessful parse *);
      signals: (IOException);
 

getNextInstance

public Instance getNextInstance()
                         throws java.io.IOException

Read the data set incrementally---get the next instance in the data set or returns null if there are no more instances to get. If the structure hasn't yet been determined by a call to getStructure then method should do so before returning the next instance in the data set. If it is not possible to read the data set incrementally (ie. in cases where the data set structure cannot be fully established before all instances have been seen) then an exception should be thrown.

Returns:

the next instance in the data set as an Instance object or null if there are no more instances to be read

Throws:

java.io.IOException - if there is an error during parsing or if getDataSet has been called on this source (either incremental or batch loading can be used, not both).

    public_normal_behavior
    {|
       requires: model_sourceSupplied == true
                 && (* successful parse *);
       modifiable: model_structureDetermined;
       ensures: model_structureDetermined == true
                && \result != null;
     also
       requires: model_sourceSupplied == true
                 && (* no further input *);
       modifiable: model_structureDetermined;
       ensures: model_structureDetermined == true
                && \result == null;
    |}
  also
    public_exceptional_behavior
    {|
       requires: model_sourceSupplied == false
                 || (* unsuccessful parse *);
       signals: (IOException);
     also
       requires: (* unable to process data set incrementally *);
       signals: (IOException);
    |}