de.gsi.math.spectra

Enum Apodization

java.lang.Object

java.lang.Enum<Apodization>

de.gsi.math.spectra.Apodization

All Implemented Interfaces:

Serializable, Comparable<Apodization>

public enum Apodization
extends Enum<Apodization>

implementation of frequenty used apodization (aka. windowing) functions reference: http://en.wikipedia.org/wiki/Apodization_function - feel free to populate this with the other (however also less frequently used) windows The array for the windows are cached. By default a WeakHashMap is used, but the cache can be replaced e.g by Cache if different caching behaviour is wanted.

Author:

rstein, akrimm

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
protected static class	Apodization.ApodizationArrayDescription private class identifying a specific buffer array, used as a key for the array cache

Enum Constant Summary

Enum Constants

Enum Constant and Description
Blackman
BlackmanHarris
BlackmanNuttall
Exponential
FlatTop
Hamming
Hann
HannExp
Nuttall
Rectangular

Method Summary

Modifier and Type	Method and Description
void	apodize(double[] data) Applies the given apodization window to the given array (in-place)
static void	apodize(double[] data, Apodization function) Applies the given apodization window to the given array (in-place)
double	getIndex(int i, int n) computes and returns the value of the apodization function for a given window index
double	getIndex(int i, int n, double m) computes and returns the value of the apodization function for a given window index
double	getIndexUncached(int i, int n) Directly computes a single window value.
String	getName()
double[]	getWindow(int n) Returns the window for a
static Map<Apodization.ApodizationArrayDescription,double[]>	getWindowCache()
static void	setWindowCache(Map<Apodization.ApodizationArrayDescription,double[]> windowCache) Changes the map used to cache the apodization windows.
static Apodization	valueOf(String name) Returns the enum constant of this type with the specified name.
static Apodization[]	values() Returns an array containing the constants of this enum type, in the order they are declared.

Methods inherited from class java.lang.Enum

clone, compareTo, equals, finalize, getDeclaringClass, hashCode, name, ordinal, toString, valueOf

Methods inherited from class java.lang.Object

getClass, notify, notifyAll, wait, wait, wait

Enum Constant Detail

Rectangular

public static final Apodization Rectangular

Hamming

public static final Apodization Hamming

Hann

public static final Apodization Hann

HannExp

public static final Apodization HannExp

Blackman

public static final Apodization Blackman

Nuttall

public static final Apodization Nuttall

BlackmanHarris

public static final Apodization BlackmanHarris

BlackmanNuttall

public static final Apodization BlackmanNuttall

FlatTop

public static final Apodization FlatTop

Exponential

public static final Apodization Exponential

Method Detail

values

public static Apodization[] values()

Returns an array containing the constants of this enum type, in the order they are declared. This method may be used to iterate over the constants as follows:

for (Apodization c : Apodization.values())
    System.out.println(c);

Returns:

an array containing the constants of this enum type, in the order they are declared

valueOf

public static Apodization valueOf(String name)

Returns the enum constant of this type with the specified name. The string must match exactly an identifier used to declare an enum constant in this type. (Extraneous whitespace characters are not permitted.)

Parameters:

name - the name of the enum constant to be returned.

Returns:

the enum constant with the specified name

Throws:

IllegalArgumentException - if this enum type has no constant with the specified name

NullPointerException - if the argument is null

getIndex

public double getIndex(int i,
                       int n)

computes and returns the value of the apodization function for a given window index

Parameters:

i - index within window

n - length of window

Returns:

value of the apodization function

getIndex

public double getIndex(int i,
                       int n,
                       double m)

computes and returns the value of the apodization function for a given window index

Parameters:

i - index within window

n - length of window

m - additional window (typ. bandwidth, power, etc)

Returns:

value of the apodization function

getIndexUncached

public double getIndexUncached(int i,
                               int n)

Directly computes a single window value. If the whole window is required multiple times it will be faster to use the cached version getIndex(int, int) provides.

Parameters:

i - index within the window

n - length of the window

Returns:

value of the apodization function

getName

public String getName()

getWindow

public double[] getWindow(int n)

Returns the window for a

Parameters:

n - window size

Returns:

a cached array containing the requested window

apodize

public void apodize(double[] data)

Applies the given apodization window to the given array (in-place)

Parameters:

data - input data

apodize

public static void apodize(double[] data,
                           Apodization function)

Applies the given apodization window to the given array (in-place)

Parameters:

data - input data

function - the apodization function to use

getWindowCache

public static Map<Apodization.ApodizationArrayDescription,double[]> getWindowCache()

Returns:

the global cache for the apodization windows

setWindowCache

public static void setWindowCache(Map<Apodization.ApodizationArrayDescription,double[]> windowCache)

Changes the map used to cache the apodization windows. The map should implement some sort of caching behaviour e.g

• WeakHashMap invalidates under memory pressure (The default)
• Cache limits retention time and number of cached entries
• custom implementation

Parameters:

windowCache - A map to use as a cache for the apodization windows