KPG1_PL2PU

Writes two-dimensional polynomial information to a POLYNOMIAL structure

Description:

This routine writes information describing a two-dimensional polynomial surface to a standard Starlink POLYNOMIAL structure, as defined in SGP/38. An empty POLYNOMIAL structure should already have been created. All floating point components within the structure are written as DOUBLE PRECISION.

It is assumed the calling programme has a one-dimensional array of coefficients, where COEFF( ( IX - 1 ) ∗ NYPAR + IY ) contains the coefficient for the (IX,IY)th term (with NYPAR being the total number of Y terms). Such a one-dimensional array is used by the NAG routines and defined in the NAG manual (see Chapter E02 on " Curve and Surface fitting" ).

This routine will convert the coefficient array to two-dimensional, flip it around and store it in the POLYNOMIAL structure so that DATA_ARRAY(IX,IY) contains the coefficient for the (IX,IY)th term (see SGP/38).

The routine will also load the TMIN and TMAX arrays with XMIN, XMAX, YMIN and YMAX. Note that these are compulsory when VARNT=’ CHEBYSHEV’ but optional when VARNT=’ SIMPLE’ . In the latter case the logical parameter LIMITS will be used to decide whether to write the limits. All the components have type _DOUBLE.

Invocation

CALL KPG1_PL2PU( LOC, VARNT, NXPAR, NYPAR, LIMITS, XMIN, XMAX, YMIN, YMAX, COEFF, VARIAN, WORK, STATUS )

Arguments

LOC = CHARACTER ∗ ( DAT__SZLOC ) (Given)
Locator to existing but empty POLYNOMIAL structure.
VARNT = CHARACTER ∗ ( ∗ ) (Given)
Variant of the polynomial (’ CHEBYSHEV’ or ’ SIMPLE’ ). (This is written but not checked).
NXPAR = INTEGER (Given)
Number of x parameters (= order of polynomial in x direction + 1)
NYPAR = INTEGER (Given)
Number of y parameters (= order of polynomial in y direction + 1)
LIMITS = LOGICAL (Given)
When VARNT=’ SIMPLE’ this logical flag may be used to control whether the TMIN and TMAX limits are written to the polynomial structure (based on the next 4 arguments). Setting LIMITS=.TRUE. will cause the limits to be written. This parameter is ignored when VARNT=’ CHEBYSHEV’ , as the limits then are compulsory.
XMIN = DOUBLE PRECISION (Given)
Minimum value along x axis for which polynomial is valid.
XMAX = DOUBLE PRECISION (Given)
Maximum value along x axis for which polynomial is valid.
YMIN = DOUBLE PRECISION (Given)
Minimum value along y axis for which polynomial is valid.
YMAX = DOUBLE PRECISION (Given)
Maximum value along y axis for which polynomial is valid.
COEFF( NXPAR ∗ NYPAR ) = DOUBLE PRECISION (Given)
Array of polynomial coefficients, in the format used by NAG routines.
VARIAN( NXPAR ∗ NYPAR ) = DOUBLE PRECISION (Given)
Array of variances of polynomial coefficients, in the format used by NAG routines.
WORK( NXPAR, NYPAR ) = DOUBLE PRECISION (Returned)
Work array used to flip the polynomial coefficients. On exit it will contain the two-dimensional array of coefficients written to the POLYNOMIAL structure.
STATUS = INTEGER (Given and Returned)
Global status value.

Notes: