I want to create a vector that contains the values of the derivative of a function f at the knot points?

I've created a function to create a polynomial approximation but now I want to add to it and one of the new arguments is a vector df(x) that contains the values of the derivative of f at the knot points

Answer 1

[David Hill]

Not really sure what you are asking. More information would be benefical to answer the question.

knotPoints=-5:5;%whatever
df=@(x)0.2*x.^2-4*x+10;%I assume you can differentiate your polynomial approximation function
v=df(knotPoints);%here is your vector