.help isinit Apr85 "Surfit Package"
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NAME
isinit -- initialize surface grid descriptor
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SYNOPSIS
include <math/surfit.h>

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isinit (sf, surface_type, xorder, yorder, xterms, ncols, nlines)
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pointer	sf		# surface descriptor
int	surface_type	# surface function
int	xorder		# order of function in x
int	yorder		# order of function in y
int	xterms		# include cross-terms? (YES/NO)
int	ncols		# number of columns in the surface grid
int	nlines		# number of lines in the surface grid
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ARGUMENTS
.ls sf    
Pointer to the surface descriptor structure.
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.ls surface_type
Fitting function. Permitted values are SF_LEGENDRE and SF_CHEBYSHEV for
the Legendre and Chebyshev polynomials and SF_SPLINE1 and SF_SPLINE3
for the linear and bicubic splines.
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.ls xorder, yorder
Order of the polynomial to be fit in x and y or the number of spline pieces to 
be fit in x and y. The orders must be greater than or equal to 1.
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.ls xterms
Include cross-terms? If xterms = YES coefficients are fit to terms containing
the cross products of x and y polynomials. Xterms defaults to YES for the
spline functions.
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.ls ncols
The number of columns in the surface grid. The surface is assumed to lie
on a rectangular grid such that 1 <= x <= ncols.
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.ls nlines
The number of lines in the surface to be grid. The surface is assumed to lie
on a rectangular grid such that 1 <= y <= nlines.
.le
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DESCRIPTION
ISINIT allocates space for the surface descriptor and the arrays and vectors
used by the numerical routines. It initializes all arrays and vectors to zero,
calculates and stores the basis functions in x and y
and returns the surface descriptor to the calling routine.
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NOTES
ISINIT must be the first SURFIT routine called.
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SEE ALSO
isfree
.endhelp
