» plot ( hanning(100) )
» help hanning

HANNING Hanning window.
W = HANNING(N) returns the N-point symmetric Hanning window 
in a column vector. 
W = HANNING(N,SFLAG) generates the N-point Hanning window 
using SFLAG window sampling. SFLAG may be either 'symmetric' 
or 'periodic'. By default, 'symmetric' window sampling is used.