csa3lxs(3NCARG)
NAME
CSA3LXS - cubic spline approximation, expanded entry for three- dimensional input, list output
SYNOPSIS
CALL CSA3LXS (NI, XI, UI, WTS, KNOTS, SMTH, NDERIV,
NO, XO, YO, ZO, 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 - Z coordinates
of the input data points. XI is dimensioned for 3 x NI.
XI(1,L) is the X coordinate, XI(2,L) is the Y coordinate,
and XI(2,L) is the Z 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 XI(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 CSA3LXS 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 3 and provides the number of knots to be
used in the X, Y, and Z directions. KNOTS(I) must be at
least 4 for I=1,3. 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 3 that specifies,
for each coordinate, whether you want functional values
(=0), first derivative values (=1), or second derivative
values (=2).
NO (integer, input) The number of coordinate values in the
output list. NO can be any positive number.
XO (real, input) An array dimensioned for NO containing the X
coordinates of the output list.
YO (real, input) An array dimensioned for NO containing the Y
coordinates of the output list.
ZO (real, input) An array dimensioned for NO containing the Z
coordinates of the output list.
UO (real, output) An array dimensioned for NO containing the
calculated function values for the output spline. UO(I) is
the calculated functional value at (XO(I),YO(I),ZO(I)) for
I=1,NO.
NWRK (integer, input) The size of the WORK array. NWRK must be
at least NK * (NK+3) where NK = KNOTS(1) * KNOTS(2) *
KNOTS(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
CSA3LXS 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 CSA3LS.
ACCESS
To use CSA3LXS, load the NCAR Graphics library ngmath.
SEE ALSO
csagrid, csa3s, csa3xs, csa3ls 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.
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