uk.ac.starlink.ttools.scheme

Class SkySimData

java.lang.Object

uk.ac.starlink.ttools.scheme.SkySimData

public class SkySimData
extends Object

Stores information required to simulate a sky catalogue. It contains data for a number of rows, each row representing a region of the sky with the capability to generate representative catalogue quantities in that region. The current implementation uses HEALPix tiles.

The data is held in arrays in memory, so that access including concurrent access will be fast. It is therefore only intended to hold information for a modest number of sky areas.

Since:

6 Aug 2020

Author:

Mark Taylor

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static class	SkySimData.Col Defines an object that can return a sample value for a given region.

Method Summary

Modifier and Type	Method and Description
SkySimData.Col	createCoordColumn(boolean isLat) Returns a column object that can give simulated sky positions.
SkySimData.Col[]	createQuantityColumns() Returns an array of column objects that can report statistically defined quantities.
HealpixTableInfo	getHealpixInfo() Returns the HEALPix setup of the statistics file on which this simulation data is based.
int	getRandomRowIndex(long seed) Returns a sky area at random.
int	getRowCount() Returns the number of sky areas represented.
static SkySimData	readData(StarTable table, HealpixTableInfo hpxInfo, String cnameWeight, String stdevSuffix) Assembles a SkySimData instance by using statistical information in a given HEALPix table (one with a row for each healpix tile).

Methods inherited from class java.lang.Object

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

Method Detail

getRowCount

public int getRowCount()

Returns the number of sky areas represented.

Returns:

row count

getHealpixInfo

public HealpixTableInfo getHealpixInfo()

Returns the HEALPix setup of the statistics file on which this simulation data is based.

Returns:

healpix info

getRandomRowIndex

public int getRandomRowIndex(long seed)

Returns a sky area at random. The returned value is weighted by the number of objects in the original data set, so that the sky distribution of the original data set can be replicated

Parameters:

seed - random seed

Returns:

weighted random row index in this data set

createCoordColumn

public SkySimData.Col createCoordColumn(boolean isLat)

Returns a column object that can give simulated sky positions.

Parameters:

isLat - true for latitude, false for longitude

createQuantityColumns

public SkySimData.Col[] createQuantityColumns()

Returns an array of column objects that can report statistically defined quantities.

Returns:

columns for quantities that can generate numeric values

readData

public static SkySimData readData(StarTable table,
                                  HealpixTableInfo hpxInfo,
                                  String cnameWeight,
                                  String stdevSuffix)
                           throws IOException

Assembles a SkySimData instance by using statistical information in a given HEALPix table (one with a row for each healpix tile). As well as a column containing the healpix index (as characterised by the HealpixTableInfo parameter), it can have pairs of column X, X<stdevSuffix> containing respectively the mean and sample standard deviation respectively of quantities per region.

Parameters:

table - table containing statistical information

hpxInfo - HEALPix characterisation of the table

cnameWeight - name of the table column containing region weight (for instance a source count)

stdevSuffix - column name suffix indicating sample standard deviation

Returns:

SkySimData instance

Throws:

IOException