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# Copyright(c) 1986 Association of Universities for Research in Astronomy Inc.
# AMED4 -- Median of four vectors. Each output point M[i] is the median of the
# four input points A[i],B[i],C[i],D[i]. The vector min and max are also
# computed and returned in the A and D vectors. The input vectors are modifed
# in place.
procedure amed4d (a, b, c, d, m, npix)
double a[ARB], b[ARB] # input vectors
double c[ARB], d[ARB] # input vectors
double m[ARB] # output vector (median)
int npix
int i
double temp
define swap {temp=$1;$1=$2;$2=temp}
begin
do i = 1, npix {
# Move the minimum value to A[i].
if (b[i] < a[i])
swap (b[i], a[i])
if (c[i] < a[i])
swap (c[i], a[i])
if (d[i] < a[i])
swap (d[i], a[i])
# Move the maximum value to D[i].
if (b[i] > d[i])
swap (b[i], d[i])
if (c[i] > d[i])
swap (c[i], d[i])
# Return the median value.
if (b[i] < c[i])
m[i] = b[i]
else
m[i] = c[i]
}
end
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