w = bartlett(L)
The window length .
The Bartlett window is very similar to a triangular window as returned by the triang function. The Bartlett window always has zeros at the first and last samples, however, while the triangular window is nonzero at those points. For L odd, the center L - 2 points of bartlett(L) are equivalent to triang(L-2).
 Oppenheim, Alan V., Ronald W. Schafer, and John R. Buck. Discrete-Time Signal Processing. Upper Saddle River, NJ: Prentice Hall, 1999.