Provided by: libncarg-dev_6.4.0-9_amd64 
NAME
CSA2XS - cubic spline approximation, expanded entry for two-dimensional input, gridded
output
SYNOPSIS
CALL CSA2XS (NI, XI, UI, WTS, KNOTS, SMTH, DERIV, NXO, NYO, XO, YO, UO, NWRK, WORK, IER)
DESCRIPTION
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.
WTS (real, input) An array dimensioned for NI containing weights for the UI values
at the input XI values, that is, WTS(L) is a weight for the value of UI(L) for
L=1,NI. If you do not desire to weight the input UI values, then set WTS(1)
to -1. The weights in the WTS array are relative and may be set to any non-
negative value. When CSA2XS is called, the weights are summed and the
individual weights are normalized so that the weight sum is unity.
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.
SMTH (real, input) A parameter that controls extrapolation into data sparse
regions. If SMTH is zero, then nothing special is done in data sparse
regions. A good first choice for SMTH is 1.
NDERIV (integer, input) An array dimensioned for 2 that specifies, for each
coordinate, whether you want functional values (=0), first derivative values
(=1), or second derivative values (=2).
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.
USAGE
CSA2XS is called to find an approximating cubic spline for two-dimensional input data.
CSA2XS is called if you want to weight the input data values, calculate derivatives, or
handle data sparse areas specially. If you do not want to do any of these three things,
then use CSA2S.
ACCESS
To use CSA2XS, load the NCAR Graphics library ngmath.
SEE ALSO
csagrid, csa2s, csa2ls, csa2lxs
Complete documentation for Csagrid is available at URL
http://ngwww.ucar.edu/ngdoc/ng/ngmath/csagrid/csahome.html
COPYRIGHT
Copyright (C) 2000
University Corporation for Atmospheric Research
The use of this Software is governed by a License Agreement.