fddm

Provides the probability density function (PDF), cumulative distribution function (CDF), and the partial derivatives of the PDF of the diffusion decision model (DDM; e.g., Ratcliff & McKoon, 2008, doi:10.1162/neco.2008.12-06-420) with across-trial variability in the drift rate. Because the PDF, its partial derivatives, and the CDF of the DDM both contain an infinite sum, they need to be approximated. 'fddm' implements all published approximations (Navarro & Fuss, 2009, doi:10.1016/j.jmp.2009.02.003; Gondan, Blurton, & Kesselmeier, 2014, doi:10.1016/j.jmp.2014.05.002; Blurton, Kesselmeier, & Gondan, 2017, doi:10.1016/j.jmp.2016.11.003; Hartmann & Klauer, 2021, doi:10.1016/j.jmp.2021.102550) plus new approximations. All approximations are implemented purely in 'C++' providing faster speed than existing packages.