c     RG operator on g(x)=G((x^2-c)/r)
c     R(g)(x)=(1/alpha)g(g(alpha*x))
c     with alpha=g(g(0))

      subroutine renor( n, f,c,r, newf)
      integer n
      double precision f(n), newf(n)
      double precision c,r
      double precision workf(n), workf1(n),aux ,alpha, gamma, beta
      aux=-c/r
      call evalu(n,f,aux,alpha)
      aux=alpha*alpha - c
      aux=aux/r
      call evalu(n,f,aux,alpha)
      gamma=alpha*alpha    
      beta= c/r
      beta=beta*(gamma - 1.0d0)
      call shift(n,f,newf, beta)
      call matscale(n,newf,gamma)
      call matmov(n,newf,workf1)
      call prod(n,newf,workf1,workf)
      workf(1) = workf(1) - c
      call matsca(n,workf,1.0d0/r)
      call compos(n,workf,f, newf)
      call matsca(n,newf,1.0d0/alpha)
      return
      end