Plot for Cubic Splines

I have created a code which works out the coefficients of each spline but I am having trouble plotting a graph using the coefficients. Matlab has problems recognising arrays like a(k) when using it to plot graphs. I don't know how to overcome this problem and have been trying for a while now.

I used the Burden and Faires, Numerical Analysis book to create the Matlab code.

Heres the code:

x=[1,2,3];

y=[2,3,5];

n = length(x);

for i=1:n-1

h(i) = x(i+1) - x(i);

end

for i=2:n-1

al(i)=((3/h(i))*(y(i+1)-y(i)))-((3/h(i-1))*(y(i)-y(i-1)));

end

l(1)=1;

m(1)=0;

z(1)=0;

for i=2:n-1

l(i)=(2*(x(i+1)-x(i-1)))-(h(i-1)*m(i-1));

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

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

end

l(n)=1;

z(n)=0;

c(n)=0;

for j=n-1:-1:1

c(j)=z(j)-(m(j)*c(j+1));

b(j)=(y(j+1)-y(j))/h(j)-(h(j)*(c(j+1)+2*c(j)))/3;

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

end

for i=1:n-1

a(i)=y(i);

end

p=x;

*for k=1:n-1

fplot('a(k)+(b(k)*(x-p(k)))+(c(k)*(x-p(k)).^2)+(d(k)*(x-p(k)).^3)',[p(k),p(k+1)])

hold on

end*

I'm having problems with the last for loop.

Answer 1

[Matt J]

for k=1:n-1

   fun=@(x) a(k)+(b(k)*(x-p(k)))+(c(k)*(x-p(k)).^2)+(d(k)*(x-p(k)).^3) ;

   fplot(fun,[p(k),p(k+1)])

   hold on

end

[Bhavik]

The hold on function isn't working properly. I'm only getting a plot of the last function. I don't get the plots of the function between x = 1 and x = 2

[Matt J]

No, the code is working fine. Add this as the very last line, if you want to see the entire plot:

axis auto