In fitteia consider the following definitions in the appropriate fields in the fitter module:

1. Independent variable: tau

2. Dependent variable: Mz

3. Expression: Mz=Minf\+(M0-Minf)*exp(-pow(fabs(tau/T1),k))

4. fitting parameters: Minf,M0,T1,k

The "\+" will produce a plot where "Mz" and the contributions "Minf", "(M0-Minf)*exp(-pow(fabs(tau/T1),k))", will be drawn.

In the above expression fabs(x) and pow(x) are functions of the C mathematical library fabs(x) calculates the absolute value of x. pow(x,k) calculates the value of x^k.

In other fitting software substitute "\+" by "+".