Built into the Wolfram Language are state-of-the-art constrained nonlinear fitting capabilities, conveniently accessed with models given directly in symbolic form. The Wolfram Language also supports unique symbolic interpolating functions that can immediately be used throughout the system to efficiently represent approximate numerical functions.

FindFit — find a general nonlinear fit, potentially including parameter constraints

Fit — linear least-squares fit to a list of symbolic functions

LeastSquares — solution to a least-squares problem in matrix form

Interpolation — find an interpolation to data in any number of dimensions

ListInterpolation  ▪  FunctionInterpolation

InterpolatingFunction — represent an approximate function to be evaluated repeatedly

InterpolatingPolynomial — construct a symbolic interpolating polynomial

Splines »

BezierFunction  ▪  BSplineFunction  ▪  ...

Peak Analysis

FindPeaks — find the positions of peaks

EstimatedBackground — estimate a smooth background

Symbolic Formula Discovery

FindFormula — attempt to find a simple symbolic formula for data