  The resistivity as function of temperature of high temperature
superconductors is very unusual and despite its importance lacks an unified
theoretical explanation. It is linear with the temperature for overdoped
compounds but it falls more quickly as the doping level decreases, and for
weakly doped samples it has a minimum, increases like an insulator before it
drops to zero at low temperatures. We show that this overall behavior can be
explained by calculations using an electronic phase segregation into two main
component phases with low and high densities. The total resistivity is
calculated by the various contributions through several random picking
processes of the local resistivities and using the Random Resistor Network
approach.
