prefuse.util
Class MathLib

java.lang.Object
  prefuse.util.MathLib

public class MathLib
extends java.lang.Object

Library of mathematical constants and methods not included in the Math class.

Author:

jeffrey heer

Field Summary

static double	LOG10 The natural logarithm of 10
static double	LOG2 The natural logarithm of 2
static double	TWO_PI The value 2 * PI

Method Summary

static double	interp(int scale, double val, double[] dist) Interpolates a value within a range using a specified scale, returning the fractional position of the value within that scale.
static double	linearInterp(double val, double min, double max) Interpolates a value between a given minimum and maximum value using a linear scale.
static double	log10(double x) The base 10 logarithm of the input value
static double	log2(double x) The base 2 logarithm of the input value
static double	logInterp(double val, double min, double max) Interpolates a value between a given minimum and maximum value using a base-10 logarithmic scale.
static double	quantile(double val, double[] quantiles) Get the quantile measure, as a value between 0 and 1, for a given value and set of quantile boundaries.
static double[]	quantiles(int n, double[] values) Compute the n-quantile boundaries for a set of values.
static double	safeLog10(double x) The "safe" base 10 logarithm of the input value, handling negative values by simply making them positive and then negating the return value.
static double	safeSqrt(double x) The "safe" square root of the input value, handling negative values by simply making them positive and then negating the return value.
static double	sqrtInterp(double val, double min, double max) Interpolates a value between a given minimum and maximum value using a square root scale.

Methods inherited from class java.lang.Object

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

Field Detail

TWO_PI

public static final double TWO_PI

The value 2 * PI

See Also:

Constant Field Values

LOG10

public static final double LOG10

The natural logarithm of 10

LOG2

public static final double LOG2

The natural logarithm of 2

Method Detail

log2

public static double log2(double x)

The base 2 logarithm of the input value

Parameters:

x - the input value

Returns:

the base 2 logarithm

log10

public static double log10(double x)

The base 10 logarithm of the input value

Parameters:

x - the input value

Returns:

the base 10 logarithm

safeLog10

public static double safeLog10(double x)

The "safe" base 10 logarithm of the input value, handling negative values by simply making them positive and then negating the return value.

Parameters:

x - the input value

Returns:

the "negative-safe" base 10 logarithm

safeSqrt

public static double safeSqrt(double x)

The "safe" square root of the input value, handling negative values by simply making them positive and then negating the return value.

Parameters:

x - the input value

Returns:

the "negative-safe" square root

interp

public static double interp(int scale,
                            double val,
                            double[] dist)

Interpolates a value within a range using a specified scale, returning the fractional position of the value within that scale.

Parameters:

scale - The scale on which to perform the interpolation, one of Constants.LINEAR_SCALE, Constants.LOG_SCALE, Constants.SQRT_SCALE, or Constants.QUANTILE_SCALE.

val - the interpolation value, a fraction between 0 and 1.0.

dist - a double array describing the distribution of the data. For the Constants.QUANTILE_SCALE option, this should be a collection of quantile boundaries, as determined by the quantiles(int, double[]) method. For any other scale type, the first value of the array must contain the minimum value of the distribution and the last value of the array must contain the maximum value of the distribution; all values in between will be ignored.

Returns:

the fractional position of the value within the scale, a double between 0 and 1.

linearInterp

public static double linearInterp(double val,
                                  double min,
                                  double max)

Interpolates a value between a given minimum and maximum value using a linear scale.

Parameters:

val - the interpolation value, a fraction between 0 and 1.0.

min - the minimum value of the interpolation range

max - the maximum value of the interpolation range

Returns:

the resulting interpolated value

logInterp

public static double logInterp(double val,
                               double min,
                               double max)

Interpolates a value between a given minimum and maximum value using a base-10 logarithmic scale.

Parameters:

val - the interpolation value, a fraction between 0 and 1.0.

min - the minimum value of the interpolation range

max - the maximum value of the interpolation range

Returns:

the resulting interpolated value

sqrtInterp

public static double sqrtInterp(double val,
                                double min,
                                double max)

Interpolates a value between a given minimum and maximum value using a square root scale.

Parameters:

val - the interpolation value, a fraction between 0 and 1.0.

min - the minimum value of the interpolation range

max - the maximum value of the interpolation range

Returns:

the resulting interpolated value

quantiles

public static double[] quantiles(int n,
                                 double[] values)

Compute the n-quantile boundaries for a set of values. The result is an n+1 size array holding the minimum value in the first entry and then n quantile boundaries in the subsequent entries.

Parameters:

n - the number of quantile boundaries. For example, a value of 4 will break up the values into quartiles, while a value of 100 will break up the values into percentiles.

values - the array of double values to divide into quantiles

Returns:

an n+1 array of doubles containing the minimum value and the quantile boundary values, in that order

quantile

public static double quantile(double val,
                              double[] quantiles)

Get the quantile measure, as a value between 0 and 1, for a given value and set of quantile boundaries. For example, if the input value is the median of the distribution described by the quantile boundaries, this method will return 0.5. As another example, if the quantile boundaries represent percentiles, this value will return the percentile ranking of the input value according to the given boundaries.

Parameters:

val - the value for which to return the quantile ranking

quantiles - an array of quantile boundaries of a distribution

Returns:

the quantile ranking, a value between 0 and 1

See Also:

quantiles(int, double[])