io.warp10.script

Class SAXUtils

java.lang.Object

io.warp10.script.SAXUtils

public class SAXUtils
extends java.lang.Object

Class contains methods related to SAX representation of time series. It includes code by Sherali Karimov (sherali.karimov@proxima-tech.com) which implements the following algorithms by Peter John Acklam (jacklam@math.uio.no): - Inverse Normal Cummulative Distribution Function Algorithm - Error Function Algorithm - Complimentary Error Function Algorithm

See Also:

http://home.online.no/~pjacklam/notes/invnorm/index.html

Field Summary

Fields

Modifier and Type	Field and Description
static int	SAX_MAX_LEVELS Maximum number of levels a SAX symbol can have.

Constructor Summary

Constructors

Constructor and Description
SAXUtils()

Method Summary

Modifier and Type	Method and Description
static byte[]	bSAX(int levels, int[] symbols) Return a binary representation (bSAX) given an array of SAX symbols and a number of levels.
static double	erf(double d)
static double	erfc(double d)
static double	erfcx(double d)
static int[]	fromBSAX(int levels, int wordlen, byte[] bsax)
static double	fromSAX(int levels, int sax, boolean random) Return an artificial value from a sax symbol and a given alphabet size (2**levels)
static double[]	getBounds(int n) Return bounds computed so each interval covers an equal area under the N(0,1) curve.
static double	getInvCDF(double d, boolean highPrecision)
static java.lang.String[]	indexable(int wordlen, int levels, byte[] bSAX) Return a String representation of the various levels of detail suitable for doing multiresolution indexing.
static double	refine(double x, double d)
static int	SAX(int levels, double value) Return a SAX symbol given a double value and a number of levels.

Methods inherited from class java.lang.Object

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

Field Detail

SAX_MAX_LEVELS

public static final int SAX_MAX_LEVELS

Maximum number of levels a SAX symbol can have. This translates to an alphabet of 2**SAX_MAX_LEVELS elements

See Also:

Constant Field Values

Constructor Detail

SAXUtils

public SAXUtils()

Method Detail

getInvCDF

public static double getInvCDF(double d,
                               boolean highPrecision)

erf

public static double erf(double d)

erfc

public static double erfc(double d)

erfcx

public static double erfcx(double d)

refine

public static double refine(double x,
                            double d)

getBounds

public static double[] getBounds(int n)

Return bounds computed so each interval covers an equal area under the N(0,1) curve.

Parameters:

n - Number of intervals to compute

Returns:

An array of bounds. Upper bound is included in the interval.

SAX

public static int SAX(int levels,
                      double value)

Return a SAX symbol given a double value and a number of levels. The returned symbol will use an alphabet of 2**level elements.

Parameters:

value -

levels -

Returns:

An int representing the SAX symbol for 'value' using 'levels'

fromSAX

public static double fromSAX(int levels,
                             int sax,
                             boolean random)

Return an artificial value from a sax symbol and a given alphabet size (2**levels)

Parameters:

levels - log2 of alphabet size

sax - Sax symbol to convert

random - Should the returned value be choosen at random in the interval

Returns:

The converted value.

Throws:

java.lang.RuntimeException - if an invalid parameter is passed

indexable

public static java.lang.String[] indexable(int wordlen,
                                           int levels,
                                           byte[] bSAX)

Return a String representation of the various levels of detail suitable for doing multiresolution indexing.

Parameters:

levels - Number of levels

bSAX - encoded

bSAX

public static byte[] bSAX(int levels,
                          int[] symbols)

Return a binary representation (bSAX) given an array of SAX symbols and a number of levels. The binary representation will consider an alphabet of 2**levels elements. The binary representation returned by the returned Function will only be meaningful in its first w * levels bits, w being the word size, i.e. number of symbols in the input array. Any extra bits will be set to 0.

Parameters:

levels - Number of levels to consider for the alphabet (2**levels elements) levels can be in the range 1 to SAX_MAX_LEVEL

Returns:

a binary representation of a SAX word (array of symbols), right padded with 0s

fromBSAX

public static int[] fromBSAX(int levels,
                             int wordlen,
                             byte[] bsax)