The function computeRandomSelection is used internally by
the CoreCollection object.
computeRandomSelection(dist, requiredN, preselected, seed)distance matrix, used for distances and implicitly defining the set of entries
the required size of the random selection
a list of preselected entries, referring to the row/column of dist
the applied seed for the randomizer
This function returns a random selection of approximately size
requiredN by choosing entries sequentually and randomly, while excluding all entries
within a certain radius of an entry chosen before, and by finding iteratively the most
appropiate radius to end up with a number close to requiredN of selected entries.