CSA3LXS - cubic spline approximation, expanded entry for
three-dimensional input, list output
CALL CSA3LXS (NI, XI, UI, WTS, KNOTS, SMTH, NDERIV,
NO, XO, YO, ZO, 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 - 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.
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.
To use CSA3LXS, load the NCAR Graphics library ngmath.
csagrid, csa3s, csa3xs, csa3ls
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.