- Simple 2D line and scatter plots.
- Operations on curves (move, scale, derivative/integral, interpolate/extrapolate, smoothing, denoise using wavelets, Fourier transform, add/subtract/multiply with another dataset).

Operations can be individually enabled/disabled, modified and removed.

- Nonlinear curve fitting:
- Fit with a sum of terms which can be independently added and enabled/disabled.
- Easily fit multiple curves sharing fit parameters.
- ODR (orthogonal distance regression) for data with both X and Y uncertainties.
- Parameter dependencies, to identify redundant parameters.
- Easy graphical setting of initial values by dragging the fit curves.

Additional analysis tools such as: find peaks, analyze peak, analyze step (e.g. glass transition), find onset point.

Do calculations and define fit functions using Python. All the functions in NumPy are available.

Unlimited

**undo/redo**of all operations.Cross-platform: runs on

**Windows, Mac OS X and Linux**.

Grafity has some features that are useful for fitting dielectric spectroscopy data:

- Built-in fit functions for DRS such as: Havriliak-Negami (various forms), KWW in freq. domain, Rouse model, VTF, Arrhenius.
- Easily fit real and imaginary part of dielectric permittivity simultaneously.
- Fast and accurate KWW function in the frequency domain (based on code from LEVMW).
- On-the-fly transform from time to frequency domain (based on F.I. Mopsik,
*J. Res. NIST*,**104**, 189 (1999)). This allows directly fitting frequency domain data with functions defined in the time domain (e.g. “Williams ansatz”) without needing to transform your data.