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# Copyright(c) 1986 Association of Universities for Research in Astronomy Inc.
include "../icombine.h"
define MINCLIP 3 # Minimum number for clipping
# IC_PCLIP -- Percentile clip
#
# 1) Find the median
# 2) Find the pixel which is the specified order index away
# 3) Use the data value difference as a sigma and apply clipping
# 4) Since the median is known return it so it does not have to be recomputed
procedure ic_pclipr (d, m, n, nimages, npts, median)
pointer d[ARB] # Data pointers
pointer m[ARB] # Image id pointers
int n[npts] # Number of good pixels
int nimages # Number of input images
int npts # Number of output points per line
real median[npts] # Median
int i, j, k, l, id, n1, n2, n3, n4, n5, nl, nh, nin, maxkeep
bool even, fp_equalr()
real sigma, r, s, t
pointer sp, resid, mp1, mp2
real med
include "../icombine.com"
begin
# There must be at least MINCLIP and more than nkeep pixels.
if (nkeep < 0)
maxkeep = max (0, nimages + nkeep)
else
maxkeep = min (nimages, nkeep)
if (nimages < max (MINCLIP, maxkeep+1) || dflag == D_NONE) {
docombine = true
return
}
call smark (sp)
call salloc (resid, nimages+1, TY_REAL)
# Set sign of pclip parameter
if (pclip < 0)
t = -1.
else
t = 1.
# If there are no rejected pixels compute certain parameters once.
if (dflag == D_ALL) {
n1 = n[1]
if (nkeep < 0)
maxkeep = max (0, n1 + nkeep)
else
maxkeep = min (n1, nkeep)
n2 = 1 + n1 / 2
even = (mod (n1, 2) == 0)
if (pclip < 0.) {
if (even)
n3 = max (1, nint (n2 - 1 + pclip))
else
n3 = max (1, nint (n2 + pclip))
} else
n3 = min (n1, nint (n2 + pclip))
nin = n1
}
# Now apply clipping.
do i = 1, npts {
# Compute median.
if (dflag == D_MIX) {
n1 = n[i]
if (nkeep < 0)
maxkeep = max (0, n1 + nkeep)
else
maxkeep = min (n1, nkeep)
if (n1 == 0) {
if (combine == MEDIAN)
median[i] = blank
next
}
n2 = 1 + n1 / 2
even = (mod (n1, 2) == 0)
if (pclip < 0) {
if (even)
n3 = max (1, nint (n2 - 1 + pclip))
else
n3 = max (1, nint (n2 + pclip))
} else
n3 = min (n1, nint (n2 + pclip))
}
j = i - 1
if (even) {
med = Memr[d[n2-1]+j]
med = (med + Memr[d[n2]+j]) / 2.
} else
med = Memr[d[n2]+j]
if (n1 < max (MINCLIP, maxkeep+1)) {
if (combine == MEDIAN)
median[i] = med
next
}
# Define sigma for clipping
sigma = t * (Memr[d[n3]+j] - med)
if (fp_equalr (sigma, 0.)) {
if (combine == MEDIAN)
median[i] = med
next
}
# Reject pixels and save residuals.
# Check if any pixels are clipped.
# If so recompute the median and reset the number of good pixels.
# Only reorder if needed.
for (nl=1; nl<=n1; nl=nl+1) {
r = (med - Memr[d[nl]+j]) / sigma
if (r < lsigma)
break
Memr[resid+nl] = r
}
for (nh=n1; nh>=1; nh=nh-1) {
r = (Memr[d[nh]+j] - med) / sigma
if (r < hsigma)
break
Memr[resid+nh] = r
}
n4 = nh - nl + 1
# If too many pixels are rejected add some back in.
# All pixels with the same residual are added.
while (n4 < maxkeep) {
if (nl == 1)
nh = nh + 1
else if (nh == n[i])
nl = nl - 1
else {
r = Memr[resid+nl-1]
s = Memr[resid+nh+1]
if (r < s) {
nl = nl - 1
r = r + TOL
if (s <= r)
nh = nh + 1
if (nl > 1) {
if (Memr[resid+nl-1] <= r)
nl = nl - 1
}
} else {
nh = nh + 1
s = s + TOL
if (r <= s)
nl = nl - 1
if (nh < n2) {
if (Memr[resid+nh+1] <= s)
nh = nh + 1
}
}
}
n4 = nh - nl + 1
}
# If any pixels are rejected recompute the median.
if (nl > 1 || nh < n1) {
n5 = nl + n4 / 2
if (mod (n4, 2) == 0) {
med = Memr[d[n5-1]+j]
med = (med + Memr[d[n5]+j]) / 2.
} else
med = Memr[d[n5]+j]
n[i] = n4
}
if (combine == MEDIAN)
median[i] = med
# Reorder if pixels only if necessary.
if (nl > 1 && (combine != MEDIAN || grow > 0)) {
k = max (nl, n4 + 1)
if (keepids) {
do l = 1, min (n1, nl-1) {
Memr[d[l]+j] = Memr[d[k]+j]
if (grow > 0) {
mp1 = m[l] + j
mp2 = m[k] + j
id = Memi[mp1]
Memi[mp1] = Memi[mp2]
Memi[mp2] = id
} else
Memi[m[l]+j] = Memi[m[k]+j]
k = k + 1
}
} else {
do l = 1, min (n1, nl - 1) {
Memr[d[l]+j] = Memr[d[k]+j]
k = k + 1
}
}
}
}
# Check if data flag needs to be reset for rejected pixels.
if (dflag == D_ALL) {
do i = 1, npts {
if (n[i] != nin) {
dflag = D_MIX
break
}
}
}
# Flag whether the median has been computed.
if (combine == MEDIAN)
docombine = false
else
docombine = true
call sfree (sp)
end
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