%BSpline.m
%Math 128B Spring 2005
%Returns B1(i,j)=Bj1(Xi)
% =j'th B-spline (with k=1) evaluated at Xi
% = characteristic function over [knots(j),knots(j+1)]

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
function	B1	= BSpline(t, knots)
%t = discretization of domain
%knots = row vector of knot locations
N	= length(knots);
M	= length(t);
TT	= repmat(t', 1, N-1);
KNOTS	= repmat(knots, M, 1);

B1(:,1:N-1)	= 0.5 * (sign(TT - KNOTS(:,1:N-1)) - sign(TT - KNOTS(:,2:N)));

return