Selection of screens for three-dimensional substructure searching

This paper describes algorithms that select a set of fragment screens for chemical substructure searching. The algorithms take as input an alphanumerically ordered list of fragments, together with their frequencies of occurrence, and produce as output a partition of this list, each portion of which contains approximately the same number of fragment occurrences. The algorithms have been developed as part of an ongoing project to develop techniques for angle-based substructure searching in files of 3-D chemical molecules; however, they are applicable to any situation requiring the selection of a set of approximately equifrequently occurring descriptors. A Pascal implementation of one of the algorithms is included on disk as SCREENS.PAS.