function [pp]=qsplinel(x,y,yp0)
n = length(x);
d = zeros(n,1);
h = zeros(n,1);
s1= zeros(n,1);
s2= ones(n,1);
t =1;
for i=2:n
d(i) = 2.*((y(i)-y(i-1))./(x(i)-x(i-1)));
h(i) = x(i)-x(i-1);
end
d(1)= yp0;
M = diag(ones(n-1,1),-1) + eye(n,n);
s1 = M\d;
while t<n
s2(t+1) = ((s1(t+1) - s1(t))./(x(t+1) - x(t)));
t=t+1;
end
a=s2(2:n)./2;
b=s1-h.*s2;
c=y'-h.*s1+1/2.*(h.^2).*s2;;
pp = mkpp(x,[a b(2:n) c(2:n)]);
end