org.apache.datasketches

Class QuantilesHelper

java.lang.Object

org.apache.datasketches.QuantilesHelper

public class QuantilesHelper
extends Object

Common static methods for quantiles sketches

Constructor Summary

Constructors

Constructor and Description
QuantilesHelper()

Method Summary

Modifier and Type	Method and Description
static int	chunkContainingPos(long[] wtArr, long pos) This is written in terms of a plain array to facilitate testing.
static long	convertToPrecedingCummulative(long[] array) Convert the weights into totals of the weights preceding each item.
static long	posOfPhi(double phi, long n) Returns the zero-based index (position) of a value in the hypothetical sorted stream of values of size n.

Methods inherited from class java.lang.Object

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

Constructor Detail

QuantilesHelper

public QuantilesHelper()

Method Detail

convertToPrecedingCummulative

public static long convertToPrecedingCummulative(long[] array)

Convert the weights into totals of the weights preceding each item. An array of {1,1,1,0} becomes {0,1,2,3}

Parameters:

array - of weights where first element is zero

Returns:

total weight

posOfPhi

public static long posOfPhi(double phi,
                            long n)

Returns the zero-based index (position) of a value in the hypothetical sorted stream of values of size n.

Parameters:

phi - the fractional position where: 0 ≤ φ ≤ 1.0.

n - the size of the stream

Returns:

the index, a value between 0 and n-1.

chunkContainingPos

public static int chunkContainingPos(long[] wtArr,
                                     long pos)

This is written in terms of a plain array to facilitate testing.

Parameters:

wtArr - the cumlative weights array consisting of chunks

pos - the position

Returns:

the index of the chunk containing the position