private ProjectedDatabase ConstructProjectedDatabase(Sequence prefix, ProjectedDatabase sourceProjectedDatabase)
{
var prefixLastItem = prefix.LastItem;
var projectedDatabase = new ProjectedDatabase(prefix);
// The count of sequences in a database which dont have to contains prefix
// and projected database can still contains some sequential pattern.
int minSequencesInProjectedDb = sourceProjectedDatabase.Size - (int)_minSupport;
for (int sid = 0, lastSid = sourceProjectedDatabase.Size; sid < lastSid; sid++)
{
// If sequence contains the last item of a prefix, project sequence and add it to db.
int itemsetIndex;
if ((itemsetIndex = sourceProjectedDatabase[sid].Contains(prefixLastItem)) >= 0)
{
var pseudoSequence = PseudoSequence.MakeProjection(sourceProjectedDatabase[sid], prefix, itemsetIndex);
if (pseudoSequence != null && pseudoSequence.IsNotEmpty)
{
projectedDatabase.Add(pseudoSequence);
continue;
}
}
// If projected database can not contains new sequential pattern stop projection sooner.
if (--minSequencesInProjectedDb < 0)
{
return(null);
}
}
return(projectedDatabase);
}
