CSA2S - cubic spline approximation, simple entry for
two-dimensional input, gridded output
CALL CSA2S (NI, XI, UI, KNOTS, NXO, ,NYO, XO, YO, UO, NWRK, WORK,
IER)
- NI
- (integer,input) The number of input data points. It must be that NI .gt. 3
and, depending on the size of KNOTS below, NI may have to be larger.
- XI
- (real, input) An array containing the X - Y coordinates of the input data
points. XI is dimensioned for 2 x NI. XI(1,L) is the X coordinate and
XI(2,L) is the Y coordinate for the input domain for L=1,NI.
- UI
- (real, input) An array dimensioned for NI containing function values at
the input XI values, that is UI(L) is the value of the input function at
the coordinate (XI(1,L),XI(2,L)) for L=1,NI.
- KNOTS
- (integer, input) The number of knots to be used in constructing the
approximation spline. KNOTS is dimensioned for 2 and provides the number
of knots to be used in the X and the Y directions. Both KNOTS(1) and
KNOTS(2) must be at least 4. The larger the values for KNOTS, the closer
the approximated curve will come to passing through the input function
values.
- NXO
- (integer, input) The number of X coordinate values in the output
grid.
- NYO
- (integer, input) The number of Y coordinate values in the output
grid.
- XO
- (real, input) An array dimensioned for NXO containing the X coordinates of
the output surface.
- YO
- (real, input) An array dimensioned for NYO containing the Y coordinates of
the output surface.
- UO
- (real, output) An array dimensioned for NXO x NYO containing the
calculated function values for the output surface. UO(I,J) is the
calculated functional value at (XO(I),YO(J)) for I=1,NXO and J=1,NYO.
- NWRK
- (integer, input) The size of the WORK array. NWRK must be at least
KNOTS(1)*KNOTS(2)*(KNOTS(1)*KNOTS(2)+3).
- WORK
- (real, input) A work array dimensioned for NWRK.
- IER
- (integer, output) An error return value. If IER is returned as 0, then no
errors were detected. If IER is non-zero, then refer to the man page for
csagrid_errors for details.
CSA2S is called to find an approximating cubic spline surface for
two-dimensional input data. If you want to weight the input data values,
calculate derivatives, or handle data sparse areas specially, then you will
need to use CSA2XS.
To use CSA2S, load the NCAR Graphics library ngmath.
csagrid, csa2xs, csa2ls, csa2lxs
Complete documentation for Csagrid is available at URL
http://ngwww.ucar.edu/ngdoc/ng/ngmath/csagrid/csahome.html
Copyright (C) 2000
University Corporation for Atmospheric Research
The use of this Software is governed by a License Agreement.