Matlab - Ayuda Interpolacion Spline Cubico

x=1:10;

y=[8 2.5 -2 0 5 2 4 7 4.5 2];

hold on

x2=1:0.5:10

y2=interp1(x,y,x2,'spline')

plot(x,y,'o',x2,y2);

function [a,b,c,d]=spline3Original_Consultar(X)

%Pasos básicos del algoritmo obtenidos del libro Análisis Numérico de 

%Richard Burden, 2a. Edición, Grupo Editorial Iberoamérica.

n=length(X(1,:));

for i=1:n;

    a(i)=X(2,i);

end

for i=1:n-1;

    h(i)=X(1,i+1)-X(1,i);

end

for i=2:n-1;

    alfa(i)=3/h(i)*(a(i+1)-a(i))-3/h(i-1)*(a(i)-a(i-1));

end

l(1)=1;

mu(1)=0;

z(1)=0;

for i=2:n-1;

    l(i)=2*(X(1,i+1)-X(1,i-1))-h(i-1)*mu(i-1);

    mu(i)=h(i)/l(i);

    z(i)=(alfa(i)-h(i-1)*z(i-1))/l(i);

end

l(n)=1;

z(n)=0;

c(n)=0;

for i=n-1:-1:1;

    c(i)=z(i)-mu(i)*c(i+1);

    b(i)=(a(i+1)-a(i))/h(i)-h(i)*(c(i+1)+2*c(i))/3;

    d(i)=(c(i+1)-c(i))/(3*h(i));

end

for i=1:n-1;

    x=X(1,i):0.5:X(1,i+1);

    m=length(x);

    fprintf('Siguientes %1.0f nodos de x \n',m);

    disp(x)

        y=a(i)+b(i)*(x-X(1,i))+c(i)*(x-X(1,i)).^2+d(i)*(x-X(1,i)).^3;

    fprintf('Imagenes de los  %1.0f nodos de x \n',m);

    disp(y)

    hold on;

    grid on;

    plot(x,y,'b'); %Plotea todos los segmentos

end

for i=1:n;

    hold on;

    plot (X(1,i),X(2,i),'*','MarkerEdgeColor','r','LineWidth',1);

    title('Interpolación por "splines" de orden 3.');

end