· Case profiles of t cases, selected randomly (using random numbers), constitute the starting configuration; in order to obtain the initial configuration, the remaining cases are distributed into t-groups.
· Case profiles of t cases, selected in a stepwise manner, constitute the starting configuration; in order to obtain the initial configuration.
When the construction starts from t case profiles, the program considers this set of t vectors as a set of t ‘starting cases’ and distributes the remaining cases according to their distance to each of the starting case.
Denote the set of t starting cases by
and the distance between groups and/or cases i and j by D(Pii,Pj).
Note that D(Pi, Pj) can be any distance - City block distance, Euclidean distance or Chi-square distance.
For each case the program calculates
There are two possibilities:
At the end of this procedure, the initial configuration is a set of t profiles
where Pj is a mean profile of all the cases belonging to the group j.
At this stage the program does not take into account weighting of cases, if any.
Here, again there are two possibilities:
then this case remains in the group Pj;
then the case i is moved from the group Pj to the group Pj, and the profiles of those two groups are recalculated as follows:
After this operation, the group Pj contains Nj-1 cases and the group Pj’ contains Nj+1 cases.
The procedure is repeated until the groups are stabilized or when the number of iterations fixed by the researcher is reached. Stability of groups is measured by the percentage of cases that do not change groups between two subsequent iterations.