Interpolation

Interpolation[data] creates an interpolating function that passes through the given data points.

Examples

Create and use interpolating functions:

data = {{0, 0}, {1, 1}, {2, 4}, {3, 9}}
f = Interpolation[data]

(* Evaluate at any point *)
f[1.5]
(* 2.25 *)

(* Plot the interpolation *)
Plot[f[x], {x, 0, 3}]

Please visit the official Wolfram Language Reference for more details.