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

  • Field Details

    • 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 Details

    • 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 Details

    • 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

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