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.help asivector Dec98 "Image Interpolator Package"
.ih
NAME
asivector -- evaluate the interpolant
.ih
SYNOPSIS
asivector (asi, x, y, npix)
.nf
pointer asi #I interpolator descriptor
real x[npix/2*npix] #I x array, 1 <= x[i] <= npix
real y[npix] #O array of interpolated values
int npix #I number of x values
.fi
.ih
ARGUMENTS
.ls asi
Pointer to the sequential interpolator descriptor structure.
.le
.ls x
Array of npix x values, or array of npix x ranges if the interpolant is
drizzle.
.le
.ls y
Array of interpolated values.
.le
.ls npix
The number of x values.
.le
.ih
DESCRIPTION
The polynomial coefficients are calculated directly from the data points
for the polynomial interpolants, and from the B-spline coefficients for
the cubic spline interpolant. The actual calculation is done by adding and
multiplying terms according to Everett's central difference interpolation
formula. The boundary extension algorithm is projection.
The sinc interpolant is computed using a range of data points around
the desired position. Look-up table sinc interpolation is computed
using the most appropriate entry in a precomputed look-up table.
The boundary extension algorithm is nearest neighbor.
The drizzle interpolant is computed by summing the data over the user
supplied X intervals.
.ih
NOTES
Checking for out of bounds and INDEF valued pixels is the responsibility of the
user. ASIINIT or ASISINIT and ASIFIT must be called before calling ASIVECTOR.
.ih
SEE ALSO
asieval, asider, arieval, arider
.endhelp
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