I want to join these cubic hermite curve, how can i do that?

clear all

a=[1,1,0;4,4,1;7,5,1;15,2,1;6,4,3]

n = input('enter the number of passing points of curve:--->>')

A= zeros(n,n); %n must be greater than 3

for i=2:n-1 % loop from 2nd to (n-1) row A(i,:) = [zeros(1,i-2),[1 4 1],zeros(1,n-i-1)]; %explicit structure of row i end

A(1,1)=1;

A(n,n)=1;

R=[0 0 0; 3*(a(3,:)-a(1,:)); 3*(a(4,:)-a(2,:));3*(a(5,:)-a(3,:));0 0 0];

X=inv(A)

T=X*R;

u=[0:0.01:1]'

U=[u.^3 u.^u u u.^0];

M=[2 -2 1 1;-3 3 -2 -1 ;0 0 1 0;1 0 0 0];

B=[a(1,:);a(2,:);0 0 0;T(2,:)];

P=U*M*B;

plot3(P(:,1),P(:,2),P(:,3));

hold on

B1=[a(2,:);a(3,:);T(2,:);T(3,:)];

P1=U*M*B1;

plot3(P1(:,1),P1(:,2),P1(:,3));

hold on

B=[a(3,:);a(4,:);T(3,:);T(4,:)];

P=U*M*B;

plot3(P(:,1),P(:,2),P(:,3));