uk.ac.starlink.ast

Class PolyMap

java.lang.Object

uk.ac.starlink.ast.AstObject

uk.ac.starlink.ast.Mapping

uk.ac.starlink.ast.PolyMap

public class PolyMap
extends Mapping

Java interface to the AST PolyMap class - map coordinates using polynomial functions. A PolyMap is a form of Mapping which performs a general polynomial transformation. Each output coordinate is a polynomial function of all the input coordinates. The coefficients are specified separately for each output coordinate. The forward and inverse transformations are defined independantly by separate sets of coefficients. If no inverse transformation is supplied, an iterative method can be used to evaluate the inverse based only on the forward transformation.

Licence

This program is free software; you can redistribute it and/or modify it under the terms of the GNU General Public Licence as published by the Free Software Foundation; either version 2 of the Licence, or (at your option) any later version.

This program is distributed in the hope that it will be useful,but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public Licence for more details.

You should have received a copy of the GNU General Public Licence along with this program; if not, write to the Free Software Foundation, Inc., 51 Franklin Street,Fifth Floor, Boston, MA 02110-1301, USA

See Also:

AST PolyMap

Nested Class Summary

Nested classes/interfaces inherited from class uk.ac.starlink.ast.Mapping

Mapping.Interpolator, Mapping.Spreader

Field Summary

Fields inherited from class uk.ac.starlink.ast.Mapping

LINEAR_INTERPOLATOR, LINEAR_SPREADER, NEAREST_INTERPOLATOR, NEAREST_SPREADER

Fields inherited from class uk.ac.starlink.ast.AstObject

AST__BAD, AST__TUNULL, pointer

Constructor Summary

Constructors

Constructor and Description
PolyMap(int nin, int nout, int ncoeff_f, double[] coeff_f, int ncoeff_i, double[] coeff_i) Creates a PolyMap.

Method Summary

Methods inherited from class uk.ac.starlink.ast.Mapping

decompose, getInvert, getNin, getNout, getReport, getTranForward, getTranInverse, invert, linearApprox, mapBox, mapSplit, rate, rebin, rebinD, rebinF, rebinI, resample, resampleB, resampleD, resampleF, resampleI, resampleL, resampleS, setInvert, setReport, simplify, tran1, tran2, tranGrid, tranN, tranP

Methods inherited from class uk.ac.starlink.ast.AstObject

annul, clear, copy, delete, equals, finalize, getAstConstantI, getB, getC, getD, getF, getI, getID, getIdent, getL, getNobject, getObjSize, getRefCount, hashCode, isThreaded, reportVersions, sameObject, set, setB, setC, setD, setF, setI, setID, setIdent, setL, show, test, tune

Methods inherited from class java.lang.Object

clone, getClass, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

PolyMap

public PolyMap(int nin,
               int nout,
               int ncoeff_f,
               double[] coeff_f,
               int ncoeff_i,
               double[] coeff_i)

Creates a PolyMap.

Parameters:

nin - The number of input coordinates.

nout - The number of output coordinates.

ncoeff_f - The number of non-zero coefficients necessary to define the forward transformation of the PolyMap. If zero is supplied, the forward transformation will be undefined.

coeff_f - An array containing "ncoeff_f*( 2 + nin )" elements. Each group of "2 + nin" adjacent elements describe a single coefficient of the forward transformation. Within each such group, the first element is the coefficient value; the next element is the integer index of the PolyMap output which uses the coefficient within its defining polynomial (the first output has index 1); the remaining elements of the group give the integer powers to use with each input coordinate value (powers must not be negative, and floating point values are rounded to the nearest integer). If "ncoeff_f" is zero, a NULL pointer may be supplied for "coeff_f".

For instance, if the PolyMap has 3 inputs and 2 outputs, each group consisting of 5 elements, A groups such as "(1.2, 2.0, 1.0, 3.0, 0.0)" describes a coefficient with value 1.2 which is used within the definition of output 2. The output value is incremented by the product of the coefficient value, the value of input coordinate 1 raised to the power 1, and the value of input coordinate 2 raised to the power 3. Input coordinate 3 is not used since its power is specified as zero. As another example, the group "(-1.0, 1.0, 0.0, 0.0, 0.0 )" describes adds a constant value -1.0 onto output 1 (it is a constant value since the power for every input axis is given as zero).

Each final output coordinate value is the sum of the "ncoeff_f" terms described by the "ncoeff_f" groups within the supplied array.

ncoeff_i - The number of non-zero coefficients necessary to define the inverse transformation of the PolyMap. If zero is supplied, the inverse transformation will be undefined.

coeff_i - An array containing "ncoeff_i*( 2 + nout )" elements. Each group of "2 + nout" adjacent elements describe a single coefficient of the inverse transformation, using the same schame as "coeff_f", except that "inputs" and "outputs" are transposed. If "ncoeff_i" is zero, a NULL pointer may be supplied for "coeff_i".

Throws:

AstException - if an error occurred in the AST library