FUNCTION FLIPUD,A
;+
;Flip a 2D array A vertically.
;-
s=Size(A)
IF s[0] LE 1 THEN RETURN,A

IF s[0] GT 2 THEN RETURN,A

k=LINDGEN(s[1],s[2])
k=s[1]*((s[2]-1)-(k/s[1]))+(k MOD s[1])
RETURN,A[k]
END