ListInterpolation

ListInterpolation[array] constructs an InterpolatingFunction object from a regular grid of values.

Examples

Interpolate a 2D array:

data = Table[Sin[x] Cos[y], {x, 0, Pi, Pi/4}, {y, 0, Pi, Pi/4}];
f = ListInterpolation[data, {{0, Pi}, {0, Pi}}]
f[1.0, 0.5]
(* 0.739 *)

1D interpolation from values:

f = ListInterpolation[{1, 4, 9, 16}];
f[2.5]
(* 6.5 *)

Please visit the official Wolfram Language Reference for more details.