program sine_animate
c     implicit none
      real x(100), y(100), x_old(100), y_old(100)
      integer pgopen

      if(pgopen('/xwin') <= 0) stop

      x_max = 5*(2*3.1415)
      delta_theta = x_max/100

      do i=1,100
        x_old(i) = i*delta_theta
        x(i) = x_old(i)
        y_old(i) = sin(x_old(i))
      end do

      x_max_1=x_max+0.5
      call pgenv(0.0,x_max_1,-1.1,1.1,0,0)

      do j=1,1000000

        do i=1,100
c         x(i) = i*delta_theta
          y(i) = sin(x(i)-0.0002*j)
        end do
        call pgbbuf
        call pgsci(0)
        call pgline(100,x_old,y_old)
        call pgsci(1)
        call pgline(100,x,y)
        call pgebuf
        do k=1,100
c         x_old(k)=x(k)
          y_old(k)=y(k)
        enddo

      enddo

      call pgclos
      end