1 files changed, 48 insertions, 0 deletions
diff --git a/sys/vops/lz/amedd.x b/sys/vops/lz/amedd.x
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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.
+
+double procedure amedd (a, npix)
+
+double	a[ARB]
+int	npix
+
+pointer	sp, aa
+double	median
+double	asokd()		# select the Kth smallest element from A
+
+begin
+	switch (npix) {
+	case 1, 2:
+	    return (a[1])
+
+	case 3:
+		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])
+		}
+
+	default:
+	    call smark (sp)
+	    call salloc (aa, npix, TY_DOUBLE)
+	    call amovd (a, Memd[aa], npix)
+	    median = asokd (Memd[aa], npix, (npix + 1) / 2)
+	    call sfree (sp)
+
+	    return (median)
+	}
+end