SURF1 - calculate values for SURF2 usage.
CALL SURF1 (M, N, X, Y, Z, IZ, ZX1, ZXM, ZY1, ZYN, ZXY11, ZXYM1,
ZXY1N, ZXYMN, ISLPSW, ZP, TEMP, SIGMA, IER)
This subroutine calculates certain values that are used by SURF2
in order to compute an interpolatory surface passing through a rectangular
grid of function values. The surface computed is a tensor product of splines
under tension. To calculate actual interpolated values, SURF2 must be
called.
- M
- (integer, input) The number of grid lines in the X direction. (M >
1)
- N
- (integer, input) The number of grid lines in the Y direction. (N >
1)
- X
- (real, input) An array containing M X coordinates for grid lines in the X
direction. These values must be strictly increasing.
- Y
- (real, input) An array containing N Y coordinates for grid lines in the Y
direction. These values must be strictly increasing.
- Z
- (real, input) An array containing M x N functional values at the grid
points; Z(I,J) contains the functional value at (X(I),Y(J)) for I=1,M and
J=1,N.
- IZ
- (integer, input) The row dimension of the matrix Z (IZ is greater than or
equal to M).
- ZX1
- (real, input) An array containing N X-partial derivatives of the function
along the line X(1), that is ZX1(J) is the X-partial derivative at point
(X(1),Y(J)) for J=1,N. This parameter may be defaulted by setting ISLPSW
appropriately.
- ZXM
- (real, input) An array containing N X-partial derivatives of the function
along the line X(M), that is ZXM(J) is the X-partial derivative at point
(X(M),Y(J)) for J=1,N. This parameter may be defaulted by setting ISLPSW
appropriately.
- ZY1
- (real, input) An array containing M Y-partial derivatives of the function
along the line Y(1), that is ZY1(I) is the Y-partial derivative at point
(X(I),Y(1)) for I=1,M. This parameter may be defaulted by setting ISLPSW
appropriately.
- ZYN
- (real, input) An array containing M Y-partial derivatives of the function
along the line Y(N), that is ZY1(I) is the Y-partial derivative at point
(X(I),Y(N)) for I=1,M. This parameter may be defaulted by setting ISLPSW
appropriately.
- ZXY11
- (real, input) The X-Y-partial derivative at (X(1),Y(1). This parameter may
be defaulted by setting ISLPSW appropriately.
- ZXYM1
- (real, input) The X-Y-partial derivative at (X(M),Y(1). This parameter may
be defaulted by setting ISLPSW appropriately.
- ZXY1N
- (real, input) The X-Y-partial derivative at (X(1),Y(N). This parameter may
be defaulted by setting ISLPSW appropriately.
- ZXYMN
- (real, input) The X-Y-partial derivative at (X(M),Y(N). This parameter may
be defaulted by setting ISLPSW appropriately.
- ISLPSW
- (integer, input) A switch to indicate which boundary derivatives are user
supplied and which should be estimated internally. Where
I1 = 0 if ZX1 is user-supplied and 1 otherwise.
I2 = 0 if ZXM is user-supplied and 1 otherwise.
I3 = 0 if ZY1 is user-supplied and 1 otherwise.
I4 = 0 if ZYN is user-supplied and 1 otherwise.
I5 = 0 if ZXY11 is user-supplied and 1 otherwise.
I6 = 0 if ZXYM1 is user-supplied and 1 otherwise.
I7 = 0 if ZXY1N is user-supplied and 1 otherwise.
I8 = 0 if ZXYMN is user-supplied and 1 otherwise.
set ISLPSW = I1 + 2*I2 + 4*I3 +8*I4 +16*I5 +32*I6 + 64*I7 +
128*I8. Then, for example, if ISLPSW=0, then all derivative information
is user-supplied and if ISLPSW=255, then all derivative information is
to be internally estimated.
- ZP
- (real, output) An array of size M x N x 3. On output this contains partial
derivatives of the surface at the given nodes. ZP is used by SURF2.
- TEMP
- (real, input) Scratch space.
- SIGMA
- (real, input) Tension factor. Values near zero result in a cubic spline;
large values (e.g. 50) result in nearly a polygonal line. A typical value
is 1.
- IER
- (integer, output) An error return value. If IER is returned as 0, then no
errors were detected.
= 1 if N is less than 2.
= 2 if X or Y values are not strictly increasing.
To use SURF1, load the NCAR Graphics library ngmath.
surf2, fitgrid_params.
Complete documentation for Fitgrid is available at URL
http://ngwww.ucar.edu/ngdoc/ng/ngmath/fitgrid/fithome.html
Copyright (C) 2000
University Corporation for Atmospheric Research
The use of this Software is governed by a License Agreement.