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# Copyright(c) 1986 Association of Universities for Research in Astronomy Inc.
# AMED -- Vector median selection. The selection is carried out in a temporary
# array, leaving the input vector unmodified. Especially demanding applications
# may wish to call the asok routine directory to avoid the call to the memory
# allocator.
PIXEL procedure amed$t (a, npix)
PIXEL a[ARB]
int npix
pointer sp, aa
PIXEL median
PIXEL asok$t() # select the Kth smallest element from A
$if (datatype == x)
real a1, a2, a3
$endif
begin
switch (npix) {
case 1, 2:
return (a[1])
case 3:
$if (datatype == x)
a1 = abs (a[1])
a2 = abs (a[2])
a3 = abs (a[3])
if (a1 < a2) {
if (a2 < a3)
return (a[2])
else if (a1 < a3)
return (a[3])
else
return (a[1])
} else {
if (a2 > a3)
return (a[2])
else if (a1 < a3)
return (a[1])
else
return (a[3])
}
$else
if (a[1] < a[2]) {
if (a[2] < a[3])
return (a[2])
else if (a[1] < a[3])
return (a[3])
else
return (a[1])
} else {
if (a[2] > a[3])
return (a[2])
else if (a[1] < a[3])
return (a[1])
else
return (a[3])
}
$endif
default:
call smark (sp)
call salloc (aa, npix, TY_PIXEL)
call amov$t (a, Mem$t[aa], npix)
median = asok$t (Mem$t[aa], npix, (npix + 1) / 2)
call sfree (sp)
return (median)
}
end
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