Interpolation based on a straight-line correlation amongst the given data points ignores all but two data points close to the unknown point, and is therefore unable to account for any effects of curvature. This is why curvilinear interpolation, a mathematically complex method, is often necessary when a highly accurate value is required. INTERP2 solves for an unknown value based on the true relationship between given values, whether that relationship is linear or nonlinear. Using the technique of the Lagrange interpolating polynomial, INTERP2 "draws" a curve through the input data points and then interpolates to expediently obtain the unknown f(x) for a known x.