1c_ftsurf(3NCARG) NCAR GRAPHICS c_ftsurf(3NCARG)
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6 c_ftsurf - 2D tension spline interpolation of rectangular data
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9 float *c_ftsurf (int, int, float *, float *, float *,
10 int, int, float *, float *, int *);
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13 float *c_ftsurf (mi, ni, xi, yi, zi, mo, no, xo, yo, ier);
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16 mi The number of grid lines in the X direction. (mi > 1)
17 ni The number of grid lines in the Y direction. (ni > 1)
19 xi Pointer to an array containing m X coordinates for grid
21 lines in the X direction.
22 yi Pointer to an array containing n Y coordinates for grid
24 lines in the Y direction.
25 zi Pointer to m x n floats which are the functional values at
27 the grid points defined by xi and yi.
28 mo The number of output values in the X direction.
30 no The number of output values in the Y direction.
32 ier The value *ier is an error flag as per:
34 = 0 -- no error.
36 = 1 -- if n is less than 2 or m is less than 2.
37 = 2 -- if X or Y values are not strictly increasing.
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41 c_ftsurf returns a pointer to an array containing mo x no floats which
42 are the interpolated values on the grid specified by the arrays xo and
43 yo.
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46 This procedure calculates an interpolatory surface passing through a
47 rectangular grid of function values. The surface computed is a tensor
48 product of splines under tension.
49 c_ftsurf is called after all of the desired values for control parame‐
51 ters have been set using the procedures c_ftseti, c_ftsetr, c_ftsetc,
52 c_ftsetfa. The control parameters that apply to c_ftsurf are: sig, zx1,
53 zxm, zy1, zyn, z11, zm1, z1n, zmn, df1, df2, df3, df4, df5, df6, df7,
54 df8
55 The value for the parameter sig specifies the tension factor. Values
57 near zero result in a cubic spline; large values (e.g. 50) result in
58 nearly a polygonal line. A typical value is 1. (the default).
59 zx1 is an array containing n X-partial derivatives of the function
61 along the line xi[0], that is zx1[j] is the X-partial derivative at
62 point (x[0],y[j]) for j=0,n-1. This parameter may be defaulted by set‐
63 ting the value for df1 appropriately. The default is to compute zx1
64 internally. Values for zx1 can be set using the procedure c_ftsetfa.
65 zxm is an array containing n X-partial derivatives of the function
67 along the line xi[m-1], that is zxm[j] is the X-partial derivative at
68 point (xi[m-1],yi[j]) for j=0,n-1. This parameter may be defaulted by
69 setting the value for df2 appropriately. The default is to compute zx2
70 internally. Values for zxm can be set using the procedure c_ftsetfa.
71 zy1 is an array containing m Y-partial derivatives of the function
73 along the line yi[0], that is zy1[j] is the Y-partial derivative at
74 point (x[i],y[0]) for i=0,m-1. This parameter may be defaulted by set‐
75 ting the value for df3 appropriately. The default is to compute zy1
76 internally. Values for zy1 can be set using the procedure c_ftsetfa.
77 zyn is an array containing m Y-partial derivatives of the function
79 along the line yi[n-1], that is zyn[j] is the Y-partial derivative at
80 point (x[i],y[n-1]) for i=0,m-1. This parameter may be defaulted by
81 setting the value for df4 appropriately. The default is to compute zyn
82 internally. Values for zyn can be set using the procedure c_ftsetfa.
83 z11, zm1, z1n, zmn specify X-Y-partial derivatives of the function at
85 the four corners (xi[0],yi[0]), (xi[m-1],yi[0]), (xi[0],yi[n-1]),
86 (xi[m-1],yi[n-1]), These parameters may be defaulted by setting the
87 values for df5, df6, df7, df8, appropriately. The default is to compute
88 z11, zm1, z1n, zmn internally.
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91 To use c_ftsurf, load the NCAR Graphics library ngmath.
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94 fitgrid_params, c_ftseti, c_ftsetr, c_ftsetc.
95 Complete documentation for Fitgrid is available at URL
97 http://ngwww.ucar.edu/ngdoc/ng/ngmath/fitgrid/fithome.html
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100 Copyright (C) 2000
101 University Corporation for Atmospheric Research
102 The use of this Software is governed by a License Agreement.
104UNIX March 1998 c_ftsurf(3NCARG)