  An affine Hecke algebra H contains a large abelian subalgebra A. The center Z
of H is the subalgebra of Weyl group invariant elements in A. The natural trace
of the affine Hecke algebra can be written as an integral of a rational $n$
form (with values in the linear dual of H) over a certain cycle in the
algebraic torus T=spec(A). We derive the Plancherel formula of the affine Hecke
algebra by localization of this integral on a certain subset of spec(Z).
