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# Copyright(c) 1986 Association of Universities for Research in Astronomy Inc.
include <math/iminterp.h>
include "im1interpdef.h"
# ASIGRL -- Procedure to find the integral of the interpolant from a to
# b be assuming that both a and b land in the array.
real procedure asigrl (asi, a, b)
pointer asi # interpolant descriptor
real a # lower limit for integral
real b # upper limit for integral
int neara, nearb, i, j, nterms, index
real deltaxa, deltaxb, accum, xa, xb, pcoeff[MAX_NDERIVS]
pointer c0ptr, n0ptr
begin
# Flip order and sign at end.
xa = a
xb = b
if (a > b) {
xa = b
xb = a
}
# Initialize.
c0ptr = ASI_COEFF(asi) - 1 + ASI_OFFSET(asi)
neara = xa
nearb = xb
accum = 0.
switch (ASI_TYPE(asi)) {
case II_NEAREST, II_SINC, II_LSINC, II_DRIZZLE:
nterms = 0
case II_LINEAR:
nterms = 1
case II_POLY3:
nterms = 4
case II_POLY5:
nterms = 6
case II_SPLINE3:
nterms = 4
}
# NEAREST_NEIGHBOR, LINEAR, SINC and LSINC are handled differently
# because of storage. Also probably good for speed in the case of
# LINEAR and NEAREST_NEIGHBOUR.
# NEAREST_NEIGHBOR
switch (ASI_TYPE(asi)) {
case II_NEAREST:
# Reset segment to center values.
neara = xa + 0.5
nearb = xb + 0.5
# Set up for first segment.
deltaxa = xa - neara
# For clarity one segment case is handled separately.
# Only one segment involved.
if (nearb == neara) {
deltaxb = xb - nearb
n0ptr = c0ptr + neara
accum = accum + (deltaxb - deltaxa) * COEFF(n0ptr)
# More than one segment.
} else {
# First segment.
n0ptr = c0ptr + neara
accum = accum + (0.5 - deltaxa) * COEFF(n0ptr)
# Middle segment.
do j = neara + 1, nearb - 1 {
n0ptr = c0ptr + j
accum = accum + COEFF(n0ptr)
}
# Last segment.
n0ptr = c0ptr + nearb
deltaxb = xb - nearb
accum = accum + (deltaxb + 0.5) * COEFF(n0ptr)
}
# LINEAR
case II_LINEAR:
# Set up for first segment.
deltaxa = xa - neara
# For clarity one segment case is handled separately.
# Only one segment is involved.
if (nearb == neara) {
deltaxb = xb - nearb
n0ptr = c0ptr + neara
accum = accum + (deltaxb - deltaxa) * COEFF(n0ptr) +
0.5 * (COEFF(n0ptr+1) - COEFF(n0ptr)) *
(deltaxb * deltaxb - deltaxa * deltaxa)
# More than one segment.
} else {
# First segment.
n0ptr = c0ptr + neara
accum = accum + (1. - deltaxa) * COEFF(n0ptr) +
0.5 * (COEFF(n0ptr+1) - COEFF(n0ptr)) *
(1. - deltaxa * deltaxa)
# Middle segment.
do j = neara + 1, nearb - 1 {
n0ptr = c0ptr + j
accum = accum + 0.5 * (COEFF(n0ptr+1) + COEFF(n0ptr))
}
# Last segment.
n0ptr = c0ptr + nearb
deltaxb = xb - nearb
accum = accum + COEFF(n0ptr) * deltaxb + 0.5 *
(COEFF(n0ptr+1) - COEFF(n0ptr)) * deltaxb * deltaxb
}
# SINC
case II_SINC, II_LSINC:
call ii_sincigrl (xa, xb, accum, COEFF(ASI_COEFF(asi) +
ASI_OFFSET(asi)), ASI_NCOEFF(asi), ASI_NSINC(asi), DX)
# DRIZZLE
case II_DRIZZLE:
if (ASI_PIXFRAC(asi) >= 1.0)
call ii_dzigrl1 (xa, xb, accum, COEFF(ASI_COEFF(asi) +
ASI_OFFSET(asi)))
else
call ii_dzigrl (xa, xb, accum, COEFF(ASI_COEFF(asi) +
ASI_OFFSET(asi)), ASI_PIXFRAC(asi))
# A higher order interpolant.
default:
# Set up for first segment.
deltaxa = xa - neara
# For clarity one segment case is handled separately.
# Only one segment involved.
if (nearb == neara) {
deltaxb = xb - nearb
n0ptr = c0ptr + neara
index = ASI_OFFSET(asi) + neara
call ii_getpcoeff (COEFF(ASI_COEFF(asi)), index, pcoeff,
ASI_TYPE(asi))
do i = 1, nterms
accum = accum + (1./i) * pcoeff[i] *
(deltaxb ** i - deltaxa ** i)
# More than one segment.
} else {
# First segment.
index = ASI_OFFSET(asi) + neara
call ii_getpcoeff (COEFF(ASI_COEFF(asi)), index, pcoeff,
ASI_TYPE(asi))
do i = 1, nterms
accum = accum + (1./i) * pcoeff[i] * (1. - deltaxa ** i)
# Middle segment.
do j = neara + 1, nearb - 1 {
index = ASI_OFFSET(asi) + j
call ii_getpcoeff (COEFF(ASI_COEFF(asi)),
index, pcoeff, ASI_TYPE(asi))
do i = 1, nterms
accum = accum + (1./i) * pcoeff[i]
}
# Last segment.
index = ASI_OFFSET(asi) + nearb
deltaxb = xb - nearb
call ii_getpcoeff (COEFF(ASI_COEFF(asi)), index, pcoeff,
ASI_TYPE(asi))
do i = 1, nterms
accum = accum + (1./i) * pcoeff[i] * deltaxb ** i
}
}
if (a < b)
return (accum)
else
return (-accum)
end
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