如何用Matlab画B-spline?

请教一下，下面是help文档：

help bspline
BSPLINE Plots a B-spline and its polynomial pieces.

BSPLINE(T) plots the B-spline with knot sequence T as well as the
polynomial pieces of which it is composed.

BSPLINE(T,WINDOW) does the plotting in the WINDOW specified, then PAUSEs.

PP = BSPLINE(T) plots nothing, but returns the ppform of the specified
B-spline, i.e., gives the same result as pp = fn2fm(spmak(t,1),'pp').

See also bsplidem, bspligui, spmak

Reference page in Help browser
doc bspline

请问一下这个T如何构造呢？

能不能举一个例子，谢谢了！