.help arider Dec98 "Image Interpolator Package"
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NAME
arider -- calculate the interpolant derivatives at x
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SYNOPSIS
include <math/iminterp.h>

arider (x, datain, npix, der, nder, interp_type)

.nf
    real	x[2]		#I x value, 1 <= x[1-2] <= npts 
    real	datain[npix]	#I array of data points
    int		npix		#I number of data points
    real	der[nder]	#O derivatives, der[1] = function value
    int		nder		#I number of derivatives, 1 + max order
    int		interp_type	#I interpolant type
.fi
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ARGUMENTS
.ls x     
Single X value, or pair of X values defining a range in the case of the
drizzle interpolant.
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.ls datain
Array of data values.
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.ls npix  
Number of data points.
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.ls der     
Array of derivatives. Der[1] contains the function value, der[2] the
first derivative, and so on.
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.ls nder
Number of derivatives. ARIDER checks that the requested number of derivatives
is sensible.  The sinc interpolant returns the function value and the first
two derivatives. The drizzle interpolant returns the function and the first
derivative.
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.ls interp_type
Interpolant type. The options are II_NEAREST, II_LINEAR, II_POLY3, II_POLY5,
II_SPLINE3, II_SINC / II_LSINC, and II_DRIZZLE. The look-up table sinc
is not supported and defaults to sinc. The sinc interpolant width is 31 pixels.
The drizzle pixel fraction is 1.0. The interpolant type definitions are found
in the package header file math/iminterp.h.
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DESCRIPTION
ARIDER permits the evaluation of the interpolant at a few randomly spaced
points within datain without the storage requirements of the sequential
version.
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NOTES
Checking for INDEF valued or out of bounds pixels is the responsibility
of the user.
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SEE ALSO
asider