uk.ac.starlink.ttools.plot2

Class ScaleType

java.lang.Object

uk.ac.starlink.ttools.plot2.ScaleType

public abstract class ScaleType
extends Object

Defines a type of axis scaling. A ScaleType is factory for Scale instances.

Since:

20 Mar 2025

Author:

Mark Taylor

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static class	ScaleType.Param Defines a numerical parameter for a ScaleType.

Field Summary

Fields

Modifier and Type	Field and Description
static ScaleType	ASINH Scale type using inverse hyperbolic sin scaling.
static ScaleType	LINEAR Linear scale type, no parameters.
static ScaleType	LOG Logarithmic scale type, no parameters.
static ScaleType	SYMLOG Scale type using so-called symmetric log scaling.
static ScaleType	TIME Time scale type, linear but with a custom rounding.

Constructor Summary

Constructors

Modifier	Constructor and Description
protected	ScaleType(String scaleName, ScaleType.Param[] params) Constructor.

Method Summary

Modifier and Type	Method and Description
abstract Scale	createScale(double[] paramValues) Constructs a scale.
static ScaleType	fromName(String name) Returns a ScaleType instance with the given name.
abstract String	getDescription() Returns an XML description of this scale type.
static ScaleType[]	getInstances() Returns a list of the general-purpose instances of this class.
String	getName() Returns the name of this type.
ScaleType.Param[]	getParams() Returns the ordered list of parameter definitions that must be supplied for scales produced by this type.
String	toString()

Methods inherited from class java.lang.Object

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

Field Detail

LINEAR

public static final ScaleType LINEAR

Linear scale type, no parameters.

LOG

public static final ScaleType LOG

Logarithmic scale type, no parameters.

SYMLOG

public static final ScaleType SYMLOG

Scale type using so-called symmetric log scaling. It can represent a wide dynamic range of values including negative ones. This idea is copied from Matplotlib's symlog scale. The region around the origin is linear, but outside that region values are scaled logarithmically, or negative logarithmically below zero.

Scales have two parameters which must both be >0:

• linthresh: defines the linear region (-linthresh..linthresh)
• linscale: ratio of graphical extent of the region (0,linthresh) to a decade in the logarithmic region

The function's derivatives are in general discontinuous at +/-linthresh

ASINH

public static final ScaleType ASINH

Scale type using inverse hyperbolic sin scaling. The scaling function is x -> asinh(x/a). This function is asymptotically linear near the origin, and asymptotically logarithmic (or negative logarithmic) far from the origin. The "linear width" parameter a, which must be >0, defines the extent of the quasi-linear region.

TIME

public static final ScaleType TIME

Time scale type, linear but with a custom rounding.

Constructor Detail

ScaleType

protected ScaleType(String scaleName,
                    ScaleType.Param[] params)

Constructor.

Parameters:

scaleName - short name for the scale type

params - numeric parameters of this scale type

Method Detail

createScale

public abstract Scale createScale(double[] paramValues)

Constructs a scale. The supplied parameter values must match those defined by the result of the {#getParams} method. Missing later values are permitted, and will be set to the default value of the relevant parameter.

Parameters:

paramValues - numeric arguments for this scale

Returns:

new scale

Throws:

IllegalArgumentException - if the values are not acceptable

getParams

public ScaleType.Param[] getParams()

Returns the ordered list of parameter definitions that must be supplied for scales produced by this type. This may be an empty array if the scale type is not parameterised.

Returns:

scale parameter specifications

getName

public String getName()

Returns the name of this type.

Returns:

type name

getDescription

public abstract String getDescription()

Returns an XML description of this scale type.

Returns:

description in XML-friendly text, but not wrapped in any element

toString

public String toString()

Overrides:

toString in class Object

getInstances

public static ScaleType[] getInstances()

Returns a list of the general-purpose instances of this class.

Returns:

instance list

fromName

public static ScaleType fromName(String name)

Returns a ScaleType instance with the given name. This is the inverse of the getName() method.

Parameters:

name - name of the scale type

Returns:

scale type matching the given name, or null