Editing Perron–Frobenius theorem (section)

====Peripheral projection====
The analysis when ''A'' is irreducible and non-negative is broadly similar. The Perron projection is still positive but there may now be other eigenvalues of modulus ρ(''A'') that negate use of the power method and prevent the powers of (1&nbsp;−&nbsp;''P'')''A'' decaying as in the primitive case whenever ρ(''A'') = 1. So we consider the '''peripheral projection''', which is the spectral projection of ''A'' corresponding to all the eigenvalues that have modulus ''ρ''(''A''). It may then be shown that the peripheral projection of an irreducible non-negative square matrix is a non-negative matrix with a positive diagonal.