1CSA2LXS(3NCARG)                  NCAR GRAPHICS                 CSA2LXS(3NCARG)
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NAME

6       CSA2LXS  -  cubic  spline  approximation, expanded entry for two-dimen‐
7       sional input, list output
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SYNOPSIS

10       CALL CSA2LXS (NI, XI, UI, WTS, KNOTS, SMTH, NDERIV,
11                     NO, XO, YO, UO, 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 CSA2LXS 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       NO          (integer,  input)  The  number  of coordinate values in the
56                   output list.  NO can be any positive number.
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58       XO          (real, input) An array dimensioned for NO containing the  X
59                   coordinates of the output list.
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61       YO          (real,  input) An array dimensioned for NO containing the Y
62                   coordinates of the output list.
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64       UO          (real, output) An array dimensioned for NO  containing  the
65                   calculated function values for the output spline.  UO(I) is
66                   the  calculated  functional  value  at  (XO(I),YO(I))   for
67                   I=1,NO.
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69       NWRK        (integer,  input) The size of the WORK array.  NWRK must be
70                   at least KNOTS(1)*KNOTS(2)*(KNOTS(1)*KNOTS(2)+3).
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72       WORK        (real, input) A work array dimensioned for NWRK.
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74       IER         (integer,  output)  An  error  return  value.   If  IER  is
75                   returned as 0, then no errors were detected. If IER is non-
76                   zero, then refer to the man  page  for  csagrid_errors  for
77                   details.
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USAGE

80       CSA2LXS  is  called if you want to weight the input data values, calcu‐
81       late derivatives, or handle data sparse areas specially.  If you do not
82       want to do any of these three things, then use CSA2LS.
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ACCESS

85       To use CSA2LXS, load the NCAR Graphics library ngmath.
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SEE ALSO

88       csagrid, csa2s, csa2xs, csa2ls,
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90       Complete documentation for Csagrid is available at URL
91       http://ngwww.ucar.edu/ngdoc/ng/ngmath/csagrid/csahome.html
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94       Copyright (C) 2000
95       University Corporation for Atmospheric Research
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97       The use of this Software is governed by a License Agreement.
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101UNIX                             January 1999                  CSA2LXS(3NCARG)
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