Editing Quasispecies model (section)

=== Note about primitive matrices ===

'''W''' being primitive means that for some integer <math> n > 0 </math>, that the <math>n^{th} </math> power of '''W''' is > 0, i.e. all the entries are positive.  If '''W''' is primitive then each type can, through a sequence of mutations (i.e. powers of '''W''') mutate into all the other types after some number of generations. '''W''' is not primitive if it is periodic, where the population can perpetually cycle through different disjoint sets of compositions, or if it is reducible, where the dominant species (or quasispecies) that develops can depend on the initial population, as is the case in the simple example given below.{{citation needed|date=August 2013}}