not-a-knot spline

i need to calculate the value of the cubic spline not a knot in the point x=1.97, the problem gives me coordinates of x=[0.0 0.5 1.0 1.5 2.0] and the function y=(sin(x)-(x+1).^2)/(x.^2+3). i don't understand why sometimes when i do y=f(x) it gives me a vector and sometimes like now it gives me only a value, and as a result it gives me an error when calculating the spline.

Answer 1

[KSSV]

x=[0.0 0.5 1.0 1.5 2.0] ;
 y = @(x) (sin(x)-(x+1).^2)./(x.^2+3)  ;
 y = y(x) ;

   xi = 1.97 ;
   yi = interp1(x,y,xi,'spline')

   plot(x,y,'b')
   hold on
   plot(xi,yi,'*r')

[Gianluca Manissero]

thanks a lot, i didn't put the point before the "/" that's why i wasn't able of solving the exercise.

[Kaloyan Pavlov]

Sorry I dont understand, if you have the function why not just calculate the function with x = 1.97?