## Abstract

We describe a fast and accurate method to compute the pressure and
equilibrium states for maps of the interval
*T:[0,1]->[0,1]* with respect to potentials
*\phi:[0,1]->R*. An approximate Ruelle-Perron-Frobenius
operator is constructed and the pressure read off as the logarithm
of the leading eigenvalue of this operator. By setting *\phi=0*,
we recover the topological entropy. The conformal measure and
the equilibrium state are computed as eigenvectors. Our approach is
extremely efficient and very simple to implement. Rigorous
convergence results are stated for piecewise expanding maps.