1CSA1XS(3NCARG)                   NCAR GRAPHICS                  CSA1XS(3NCARG)
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NAME

6       CSA1XS - cubic spline approximation, expanded entry for one-dimensional
7       input
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SYNOPSIS

10       CALL CSA1XS (NI, XI, YI, WTS, KNOTS, SMTH, DERIV,  NO,  XO,  YO,  NWRK,
11       WORK, IER)
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DESCRIPTION

14       NI          (integer,input) The number of input data points. It must be
15                   that NI > 3 and, depending on the size of KNOTS  below,  NI
16                   may have to be larger.
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18       XI          (real,  input) An array dimensioned for NI containing the X
19                   coordinates of the input data points.
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21       YI          (real, input) An array dimensioned for NI containing  func‐
22                   tion  values  at the input XI values, that is, YI(L) is the
23                   value of the input function at XI(L) for L=1,NI.
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25       WTS         (real,  input)  An  array  dimensioned  for  NI  containing
26                   weights  for the YI values at the input XI values, that is,
27                   WTS(L) is a weight for the value of YI(L) for  L=1,NI.   If
28                   you  do  not desire to weight the input YI values, then set
29                   WTS(1) to -1.  The weights in the WTS  array  are  relative
30                   and  may  be set to any non-negative value.  When CSA1XS is
31                   called, the weights are summed and the  individual  weights
32                   are normalized so that the weight sum is unity.
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34       KNOTS       (integer,  input)  The  number  of knots to be used in con‐
35                   structing the approximation spline.  KNOTS must be at least
36                   4.  The larger the value for KNOTS, the closer the approxi‐
37                   mated curve will come to passing through the input function
38                   values.
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40       SMTH        (real,  input) A parameter that controls extrapolation into
41                   data sparse regions.  If SMTH is zero, then nothing special
42                   is  done  in  data sparse regions.  A good first choice for
43                   SMTH is 1.
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45       NDERIV      (integer, input) Specifies whether you want functional val‐
46                   ues (NDERIV=0), first derivative values (NDERIV=1), or sec‐
47                   ond derivative values (NDERIV=2).
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49       NO          (integer, input) The number of values to be calculated  for
50                   the output curve.
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52       XO          (real,  input) An array dimensioned for NO containing the X
53                   coordinates of the output curve.
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55       YO          (real, output) An array dimensioned for NO  containing  the
56                   calculated function values for the output curve.
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58       NWRK        (integer,  input) The size of the WORK array.  NWRK must be
59                   at least KNOTS*(KNOTS+3).
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61       WORK        (real, input) A work array dimensioned for NWRK.
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63       IER         (integer,  output)  An  error  return  value.   If  IER  is
64                   returned as 0, then no errors were detected. If IER is non-
65                   zero, then refer to the man  page  for  csagrid_errors  for
66                   details.
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USAGE

69       CSA1XS  is  called to find an approximating cubic spline for one-dimen‐
70       sional input data.  CSA1XS is called if you want to  weight  the  input
71       data  values,  calculate  derivatives, or handle data sparse areas spe‐
72       cially.  If you do not want to do any of these three things,  then  use
73       CSA1S.
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ACCESS

76       To use CSA1XS, load the NCAR Graphics library ngmath.
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SEE ALSO

79       csagrid, csa1s, csa1ls, csa1lxs
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81       Complete documentation for Csagrid is available at URL
82       http://ngwww.ucar.edu/ngdoc/ng/ngmath/csagrid/csahome.html
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85       Copyright (C) 2000
86       University Corporation for Atmospheric Research
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88       The use of this Software is governed by a License Agreement.
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92UNIX                             January 1999                   CSA1XS(3NCARG)
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