program anim_circle
      i_dummy=pgopen('/xwin')
      xmin=-5
      xmax=5
      ymin=-5
      ymax=5
      call pgenv(xmin,xmax,ymin,ymax,1,0)
      call pgsfs(2)
      xini=0
      yini=0
      do i=1,100000
        x=xini
        y=yini
        r=2.0+sin(0.002*i)
        call pgbbuf
          call pgsci(0)
          call pgcirc(xold,yold,rold)
          call pgsci(1)
          call pgcirc(x,y,r)
        call pgebuf 
        xold=x
        yold=y
        rold=r
      end do

      end