ncarg_csa2xs(3)

1CSA2XS(3NCARG)                   NCAR GRAPHICS                  CSA2XS(3NCARG)
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NAME

6       CSA2XS - cubic spline approximation, expanded entry for two-dimensional
7       input, gridded output
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SYNOPSIS

10       CALL CSA2XS (NI, XI, UI, WTS, KNOTS, SMTH, DERIV, NXO, NYO, XO, YO, UO,
11       NWRK, WORK, IER)
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DESCRIPTION

14       NI          (integer,input) The number of input data points. It must be
15                   that NI .gt. 3 and, depending on the size of  KNOTS  below,
16                   NI may have to be larger.
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18       XI          (real,  input) An array containing the X - Y coordinates of
19                   the input data points.  XI  is  dimensioned  for  2  x  NI.
20                   XI(1,L) is the X coordinate and XI(2,L) is the Y coordinate
21                   for the input domain for L=1,NI.
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23       UI          (real, input) An array dimensioned for NI containing  func‐
24                   tion  values  at  the input XI values, that is UI(L) is the
25                   value   of   the   input   function   at   the   coordinate
26                   (XI(1,L),XI(2,L)) for L=1,NI.
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28       WTS         (real,  input)  An  array  dimensioned  for  NI  containing
29                   weights for the UI values at the input XI values, that  is,
30                   WTS(L)  is  a weight for the value of UI(L) for L=1,NI.  If
31                   you do not desire to weight the input UI values,  then  set
32                   WTS(1)  to  -1.   The weights in the WTS array are relative
33                   and may be set to any non-negative value.  When  CSA2XS  is
34                   called,  the  weights are summed and the individual weights
35                   are normalized so that the weight sum is unity.
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37       KNOTS       (integer, input) The number of knots to  be  used  in  con‐
38                   structing  the  approximation spline.  KNOTS is dimensioned
39                   for 2 and provides the number of knots to be used in the  X
40                   and  the  Y directions.  Both KNOTS(1) and KNOTS(2) must be
41                   at least 4.  The larger the values for  KNOTS,  the  closer
42                   the  approximated  curve  will  come to passing through the
43                   input function values.
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45       SMTH        (real, input) A parameter that controls extrapolation  into
46                   data sparse regions.  If SMTH is zero, then nothing special
47                   is done in data sparse regions.  A good  first  choice  for
48                   SMTH is 1.
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50       NDERIV      (integer, input) An array dimensioned for 2 that specifies,
51                   for each coordinate,  whether you  want  functional  values
52                   (=0),  first  derivative  values (=1), or second derivative
53                   values (=2).
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55       NXO         (integer, input) The number of X coordinate values  in  the
56                   output grid.
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58       NYO         (integer,  input)  The number of Y coordinate values in the
59                   output grid.
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61       XO          (real, input) An array dimensioned for NXO containing the X
62                   coordinates of the output surface.
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64       YO          (real, input) An array dimensioned for NYO containing the Y
65                   coordinates of the output surface.
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67       UO          (real, output) An array dimensioned for NXO x NYO  contain‐
68                   ing  the calculated function values for the output surface.
69                   UO(I,J) is the calculated functional value at (XO(I),YO(J))
70                   for I=1,NXO and J=1,NYO.
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72       NWRK        (integer,  input) The size of the WORK array.  NWRK must be
73                   at least KNOTS(1)*KNOTS(2)*(KNOTS(1)*KNOTS(2)+3).
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75       WORK        (real, input) A work array dimensioned for NWRK.
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77       IER         (integer,  output)  An  error  return  value.   If  IER  is
78                   returned as 0, then no errors were detected. If IER is non-
79                   zero, then refer to the man  page  for  csagrid_errors  for
80                   details.
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USAGE

83       CSA2XS  is  called to find an approximating cubic spline for two-dimen‐
84       sional input data.  CSA2XS is called if you want to  weight  the  input
85       data  values,  calculate  derivatives, or handle data sparse areas spe‐
86       cially.  If you do not want to do any of these three things,  then  use
87       CSA2S.
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ACCESS

90       To use CSA2XS, load the NCAR Graphics library ngmath.
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COPYRIGHT

99       Copyright (C) 2000
100       University Corporation for Atmospheric Research
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102       This  documentation  is  free  software; you can redistribute it and/or
103       modify it under the terms of the GNU General  Public  License  as  pub‐
104       lished  by  the  Free  Software  Foundation;  either  version  2 of the
105       License, or (at your option) any later version.
106
107       This software is distributed in the hope that it will  be  useful,  but
108       WITHOUT  ANY  WARRANTY;  without  even  the  implied  warranty  of MER‐
109       CHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU  General
110       Public License for more details.
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112       You should have received a copy of the GNU General Public License along
113       with this software; if not, write  to  the  Free  Software  Foundation,
114       Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA.
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119UNIX                             January 1999                   CSA2XS(3NCARG)

NAME

SYNOPSIS

DESCRIPTION

USAGE

ACCESS

SEE ALSO

COPYRIGHT