1SURF1(3NCARG)                    NCAR GRAPHICS                   SURF1(3NCARG)
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NAME

6       SURF1 - calculate values for SURF2 usage.
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SYNOPSIS

9       CALL SURF1 (M, N, X, Y, Z, IZ, ZX1, ZXM, ZY1, ZYN, ZXY11, ZXYM1, ZXY1N,
10       ZXYMN, ISLPSW, ZP, TEMP, SIGMA, IER)
11
12       This subroutine calculates certain values that are  used  by  SURF2  in
13       order to compute an interpolatory surface passing through a rectangular
14       grid of function values. The surface computed is a  tensor  product  of
15       splines  under  tension. To calculate actual interpolated values, SURF2
16       must be called.
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DESCRIPTION

19       M           (integer, input) The number of grid lines in the  X  direc‐
20                   tion. (M > 1)
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22       N           (integer,  input)  The number of grid lines in the Y direc‐
23                   tion. (N > 1)
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25       X           (real, input) An array containing M X coordinates for  grid
26                   lines  in  the  X  direction. These values must be strictly
27                   increasing.
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29       Y           (real, input) An array containing N Y coordinates for  grid
30                   lines  in  the  Y  direction. These values must be strictly
31                   increasing.
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33       Z           (real, input) An array containing M x N  functional  values
34                   at the grid points; Z(I,J) contains the functional value at
35                   (X(I),Y(J)) for I=1,M and J=1,N.
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37       IZ          (integer, input) The row dimension of the matrix Z  (IZ  is
38                   greater than or equal to M).
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40       ZX1         (real,  input)  An array containing N X-partial derivatives
41                   of the function along the line X(1), that is ZX1(J) is  the
42                   X-partial  derivative  at point (X(1),Y(J)) for J=1,N. This
43                   parameter may be defaulted by setting ISLPSW appropriately.
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45       ZXM         (real, input) An array containing N  X-partial  derivatives
46                   of  the function along the line X(M), that is ZXM(J) is the
47                   X-partial derivative at point (X(M),Y(J)) for  J=1,N.  This
48                   parameter may be defaulted by setting ISLPSW appropriately.
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50       ZY1         (real,  input)  An array containing M Y-partial derivatives
51                   of the function along the line Y(1), that is ZY1(I) is  the
52                   Y-partial  derivative  at point (X(I),Y(1)) for I=1,M. This
53                   parameter may be defaulted by setting ISLPSW appropriately.
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55       ZYN         (real, input) An array containing M  Y-partial  derivatives
56                   of  the function along the line Y(N), that is ZY1(I) is the
57                   Y-partial derivative at point (X(I),Y(N)) for  I=1,M.  This
58                   parameter may be defaulted by setting ISLPSW appropriately.
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60       ZXY11       (real,  input)  The  X-Y-partial  derivative at (X(1),Y(1).
61                   This parameter may be defaulted by setting ISLPSW appropri‐
62                   ately.
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64       ZXYM1       (real,  input)  The  X-Y-partial  derivative at (X(M),Y(1).
65                   This parameter may be defaulted by setting ISLPSW appropri‐
66                   ately.
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68       ZXY1N       (real,  input)  The  X-Y-partial  derivative at (X(1),Y(N).
69                   This parameter may be defaulted by setting ISLPSW appropri‐
70                   ately.
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72       ZXYMN       (real,  input)  The  X-Y-partial  derivative at (X(M),Y(N).
73                   This parameter may be defaulted by setting ISLPSW appropri‐
74                   ately.
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76       ISLPSW      (integer, input) A switch to indicate which boundary deriv‐
77                   atives are user supplied  and  which  should  be  estimated
78                   internally. Where
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80                   I1 = 0 if ZX1 is user-supplied and 1 otherwise.
81                   I2 = 0 if ZXM is user-supplied and 1 otherwise.
82                   I3 = 0 if ZY1 is user-supplied and 1 otherwise.
83                   I4 = 0 if ZYN is user-supplied and 1 otherwise.
84                   I5 = 0 if ZXY11 is user-supplied and 1 otherwise.
85                   I6 = 0 if ZXYM1 is user-supplied and 1 otherwise.
86                   I7 = 0 if ZXY1N is user-supplied and 1 otherwise.
87                   I8 = 0 if ZXYMN is user-supplied and 1 otherwise.
88
89                   set ISLPSW = I1 + 2*I2 + 4*I3 +8*I4 +16*I5 +32*I6 + 64*I7 +
90                   128*I8. Then, for example, if ISLPSW=0, then all derivative
91                   information  is  user-supplied  and if ISLPSW=255, then all
92                   derivative information is to be internally estimated.
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94       ZP          (real, output) An array of size M x N x 3. On  output  this
95                   contains  partial  derivatives  of the surface at the given
96                   nodes. ZP is used by SURF2.
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98       TEMP        (real, input) Scratch space.
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100       SIGMA       (real, input) Tension factor. Values near zero result in  a
101                   cubic  spline;  large  values  (e.g. 50) result in nearly a
102                   polygonal line. A typical value is 1.
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104       IER         (integer, output) An error return value. If IER is returned
105                   as 0, then no errors were detected.
106
107                   = 1 if N is less than 2.
108                   = 2 if X or Y values are not strictly increasing.
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ACCESS

111       To use SURF1, load the NCAR Graphics library ngmath.
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SEE ALSO

114       surf2, fitgrid_params.
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116       Complete documentation for Fitgrid is available at URL
117       http://ngwww.ucar.edu/ngdoc/ng/ngmath/fitgrid/fithome.html
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120       Copyright (C) 2000
121       University Corporation for Atmospheric Research
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123       The use of this Software is governed by a License Agreement.
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127UNIX                              March 1998                     SURF1(3NCARG)
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