Phase diagram can be constructed that show the effect of more than two variables on the phase of a substance. Phase diagrams can use other variables in addition to or in place of temperature, pressure and composition, for example the strength of an applied electrical or magnetic field, and they can also involve substances that take on more than just three states of matter. One type of phase diagram plots temperature against the relative concentrations of two substances in a mixture called a "binary phase diagram", as shown at right. Such a mixture can be either a solid solution, eutectic or peritectic,
Phase-type distribution (the non-homogeneous case). The mixture of two Erlang distribution with parameter "E"(3,β), "E"(3,β) and (α,α) (such that α + α = 1 and for each "i", α ≥ 0) can be represented as a phase type distribution with and The Coxian distribution is a generalisation of the hypoexponential distribution. Instead of only being able to enter the absorbing state from state "k" it can be reached from any phase. The phase-type representation is given by, and where 0 < "p"...,"p" ≤ 1. In the case where all "p" = 1 we have the hypoexponential distribution. The Coxian distribution is extremely