uk.ac.starlink.ttools.plot2.layer

Class Normalisation

java.lang.Object

uk.ac.starlink.ttools.plot2.layer.Normalisation

@Equality
public abstract class Normalisation
extends Object

Defines normalisation modes for histogram-like plots.

Since:

19 Feb 2015

Author:

Mark Taylor

Field Summary

Fields

Modifier and Type	Field and Description
static Normalisation	AREA The total area of histogram bars is normalised to unity.
static Normalisation	HEIGHT The total height of histogram bars is normalised to unity.
static Normalisation	MAXIMUM Height of the tallest histogram bar is normalised to unity.
static Normalisation	NONE No normalisation is performed.
static Normalisation	UNIT Bars scaled by inverse bin width.

Constructor Summary

Constructors

Modifier	Constructor and Description
protected	Normalisation(String name, String description) Constructor.

Method Summary

Modifier and Type	Method and Description
String	getDescription() Returns a short description of this mode.
static Normalisation[]	getKnownValues() Returns the Normalisation instances defined by this class.
abstract double	getScaleFactor(double sum, double max, double binWidth, Combiner.Type ctype, boolean isCumulative) Returns the value by which all bins should be scaled to achieve normalisation for a given data set.
String	toString()

Methods inherited from class java.lang.Object

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

Field Detail

NONE

public static final Normalisation NONE

No normalisation is performed.

AREA

public static final Normalisation AREA

The total area of histogram bars is normalised to unity.

UNIT

public static final Normalisation UNIT

Bars scaled by inverse bin width.

MAXIMUM

public static final Normalisation MAXIMUM

Height of the tallest histogram bar is normalised to unity.

HEIGHT

public static final Normalisation HEIGHT

The total height of histogram bars is normalised to unity.

Constructor Detail

Normalisation

protected Normalisation(String name,
                        String description)

Constructor.

Parameters:

name - mode name

description - short description

Method Detail

getDescription

public String getDescription()

Returns a short description of this mode.

Returns:

description

getScaleFactor

public abstract double getScaleFactor(double sum,
                                      double max,
                                      double binWidth,
                                      Combiner.Type ctype,
                                      boolean isCumulative)

Returns the value by which all bins should be scaled to achieve normalisation for a given data set.

The binWidth should at least make sense in terms of screen area. For linear X axis, it should be in data units, but for logarithmic X axis it may have to be in log(data units). The binWidth is only used by AREA and UNIT modes.

For cumulative plots, all the modes except NONE behave the same, normalising the total value to unity. The Combiner.Type may result in scaling the values by the inverse of the bin width. However, that is sometimes done anyway (UNIT and AREA modes), so for those cases it's ignored, since you don't want to apply that correction twice.

Parameters:

sum - total height of all histogram bars

max - height of tallest histogram bar

binWidth - constant linear width of histogram bars, or NaN

ctype - combiner type used to populate bins

isCumulative - true iff the plot is cumulative

toString

public String toString()

Overrides:

toString in class Object

getKnownValues

public static Normalisation[] getKnownValues()

Returns the Normalisation instances defined by this class.

Returns:

list of normalisation instances