uk.ac.starlink.ttools.plot2.layer

Class BinMapper

java.lang.Object

uk.ac.starlink.ttools.plot2.layer.BinMapper

@Equality
public abstract class BinMapper
extends Object

Maps axis values to bin indices.

Since:

16 Jan 2017

Author:

Mark Taylor

Constructor Summary

Constructors

Constructor and Description
BinMapper()

Method Summary

Modifier and Type	Method and Description
static BinMapper	createMapper(boolean log, double binWidth, double binPhase, double point) Returns a BinMapper instance.
abstract int	getBinIndex(double value) Returns the bin index for a given value.
abstract double[]	getBinLimits(int index) Returns the bin limits for a given bin index.
static double	log(double val) Logarithm function, used for transforming values on logarithmic X axis.

Methods inherited from class java.lang.Object

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

Constructor Detail

BinMapper

public BinMapper()

Method Detail

getBinIndex

public abstract int getBinIndex(double value)

Returns the bin index for a given value. In case of an invalid value (NaN, or non-positive for log mapper), behaviour is undefined (quite likely zero will be returned).

Parameters:

value - valid axis value

Returns:

bin index

getBinLimits

public abstract double[] getBinLimits(int index)

Returns the bin limits for a given bin index.

Parameters:

index - bin index

Returns:

(lower,upper) bin limits

createMapper

public static BinMapper createMapper(boolean log,
                                     double binWidth,
                                     double binPhase,
                                     double point)

Returns a BinMapper instance.

Notional bin boundaries are for log=false:

   binWidth*(0+binPhase), binWidth*(1+binPhase), ...
 

and for log=true:

   binWidth**(0+binPhase), binWidth**(1+binPhase), ...
 

The point parameter is used internally to determine the zero point of the bins. In principle this should make no difference to behaviour, but in case that the data is situated a very long way from 1, setting it close to the actual data point locations may avoid rounding errors.

Parameters:

log - false for linear axis scaling, true for logarithmic

binWidth - width of each bin; this is additive for linear and multiplicative for logarithmic scaling

binPhase - determines sub-bin boundary shifts along axis, normally in range 0..1

point - representative point on axis near which bins are situated

log

public static double log(double val)

Logarithm function, used for transforming values on logarithmic X axis.

Parameters:

val - value

Returns:

log to base 10 of val