1CSA3XS(3NCARG)                   NCAR GRAPHICS                  CSA3XS(3NCARG)
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NAME

6       CSA3XS  -  cubic  spline approximation, expanded entry for three-dimen‐
7       sional input
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SYNOPSIS

10       CALL CSA3XS (NI, XI, UI, WTS, KNOTS, SMTH, NDERIV,
11                    NXO, ,NYO, NZO, XO, YO, ZO, UO, NWRK,
12                    WORK, IER)
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DESCRIPTION

15       NI          (integer,input) The number of input data points. It must be
16                   that  NI  .gt. 3 and, depending on the size of KNOTS below,
17                   NI may have to be larger.
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19       XI          (real, input) An array containing the X - Y - Z coordinates
20                   of  the  input  data points.  XI is dimensioned for 3 x NI.
21                   XI(1,L) is the X coordinate, XI(2,L) is the  Y  coordinate,
22                   and  XI(2,L)  is  the Z coordinate for the input domain for
23                   L=1,NI.
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25       UI          (real, input) An array dimensioned for NI containing  func‐
26                   tion  values  at the input XI values, that is, UI(L) is the
27                   value of the input function at XI(L) for  L=1,NI.   through
28                   the input function values.
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30       WTS         (real,  input)  An  array  dimensioned  for  NI  containing
31                   weights for the UI values at the input XI values, that  is,
32                   WTS(L)  is  a weight for the value of UI(L) for L=1,NI.  If
33                   you do not desire to weight the input UI values,  then  set
34                   WTS(1)  to  -1.   The weights in the WTS array are relative
35                   and may be set to any non-negative value.  When  CSA3XS  is
36                   called,  the  weights are summed and the individual weights
37                   are normalized so that the weight sum is unity.
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39       KNOTS       (integer, input) The number of knots to  be  used  in  con‐
40                   structing  the  approximation spline.  KNOTS is dimensioned
41                   for 3 and provides the number of knots to be used in the X,
42                   Y, and  Z directions.  Both KNOTS(I) must be at least 4 for
43                   I=1,3.  The larger the values for  KNOTS,  the  closer  the
44                   approximated  curve  will come to passing through the input
45                   function values.
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47       SMTH        (real, input) A parameter that controls extrapolation  into
48                   data sparse regions.  If SMTH is zero, then nothing special
49                   is done in data sparse regions.  A good  first  choice  for
50                   SMTH is 1.
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52       NDERIV      (integer, input) An array dimensioned for 3 that specifies,
53                   for each coordinate,  whether you  want  functional  values
54                   (=0),  first  derivative  values (=1), or second derivative
55                   values (=2).
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57       NXO         (integer, input) The number of X coordinate values  in  the
58                   output grid.
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60       NYO         (integer,  input)  The number of Y coordinate values in the
61                   output grid.
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63       NZO         (integer, input) The number of Z coordinate values  in  the
64                   output grid.
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66       XO          (real, input) An array dimensioned for NXO containing the X
67                   coordinates of the output spline.
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69       YO          (real, input) An array dimensioned for NYO containing the Y
70                   coordinates of the output spline.
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72       ZO          (real, input) An array dimensioned for NZO containing the Z
73                   coordinates of the output spline.
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75       UO          (real, output) An array dimensioned for NXO  x  NYO  x  NZO
76                   containing  the  calculated  function values for the output
77                   function.  UO(I,J,K) is the calculated functional value  at
78                   (XO(I), YO(J), ZO(K)) for I=1,NXO and J=1,NYO and K=1,NZO.
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80       NWRK        (integer,  input) The size of the WORK array.  NWRK must be
81                   at least NK * (NK+3) where  NK  =  KNOTS(1)  *  KNOTS(2)  *
82                   KNOTS(3).
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84       WORK        (real, input) A work array dimensioned for NWRK.
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86       IER         (integer,  output)  An  error  return  value.   If  IER  is
87                   returned as 0, then no errors were detected. If IER is non-
88                   zero,  then  refer  to  the man page for csagrid_errors for
89                   details.
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USAGE

92       CSA3XS is called to find an approximating cubic spline for three-dimen‐
93       sional  input  data.   CSA3XS is called if you want to weight the input
94       data values, calculate derivatives, or handle data  sparse  areas  spe‐
95       cially.   If  you do not want to do any of these three things, then use
96       CSA3S.
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ACCESS

99       To use CSA3XS, load the NCAR Graphics library ngmath.
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SEE ALSO

102       csagrid, csa3s, csa3ls, csa3lxs
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104       Complete documentation for Csagrid is available at URL
105       http://ngwww.ucar.edu/ngdoc/ng/ngmath/csagrid/csahome.html
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108       Copyright (C) 2000
109       University Corporation for Atmospheric Research
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111       The use of this Software is governed by a License Agreement.
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115UNIX                             January 1999                   CSA3XS(3NCARG)
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