IMPORTANT NOTE -------------- Version 2.4.4 of the PE Toolbox changes an important internal parameter in the hd-PS variable selection process. In prior versions, a code had to occur at least 100 times across the population in order to be considered for inclusion. This version removes that requirement, but to maintain compatibility with older versions, a minimum frequency can be imposed by setting the option: frequency_min = 100 Other values of minimum frequency can also be set as desired. Setting the minimum to 0 indicates that no minimum threshold must be met.