In a dispersion analysis the target function *f* (*θ*) is the chi-squared equation

where *i* is the summation index,
R_{2eff} is the experimental relaxation data which belongs to the data set R and includes the
R_{2eff} and
R_{1ρ} values for all experiments at all magnetic field strengths,
R_{2eff}(*θ*) is the back calculated relaxation data belonging to the set R(*θ*), and *σ*_{i} is the experimental
R_{2eff}/R_{1ρ} error.
For standard optimisation, the summation index ranges over the relaxation data of an individual spin.
However this can be changed with clustering whereby the relaxation data from a group of spin systems are optimised using a shared set of parameters.

The relax user manual (PDF), created 2016-10-28.