program graph2
   implicit none
   call init
   call viewport(0.2,0.2,0.8,0.8)
   call xyworld(0.0,-1.0,1.0,1.0)
   call frame
   call plotd
   call fin
   stop
   end

real function f(x)
   implicit none
   real(4) x,pi
   pi=atan(1.0)*4.0
   f=exp(-x)*sin(4.0*pi*x)
   return
   end

subroutine plotd
   implicit none
   real(4),dimension(0:20)::x1,y1
   integer i
   integer,parameter::n=20
   real(4) f
   do i=0,n
      x1(i)=real(i)/real(n)
      y1(i)=f(x1(i))
   end do
   call linewidth(1.5)
   call linety(1)
   call setgray(0.0)
   call plot(x1(0),y1(0),3)
   do i=1,n-2
      call spline(x1(i-1),y1(i-1),x1(i),y1(i),x1(i+1),y1(i+1),x1(i+2),y1(i+2),-1)
   end do
   call spline(x1(n-3),y1(n-3),x1(n-2),y1(n-2),x1(n-1),y1(n-1),x1(n),y1(n),0)
   call spline(x1(n-3),y1(n-3),x1(n-2),y1(n-2),x1(n-1),y1(n-1),x1(n),y1(n),1)
   call stroke
   return
   end

subroutine frame
   implicit none
   real(4) x,y,dx,dy
   integer,parameter::nx=2,ny=2
   integer ix,iy
   call linewidth(1.0)
   call rect(0.0,-1.0,1.0,1.0)
   call stroke
   do ix=1,nx*10-1
      x=real(ix)/real(nx*10)
      dy=1.0
      if(ix/10*10==ix)then
         call setgray(0.5)
      else
         call setgray(0.8)
      end if
      call plot(x,-dy,3)
      call plot(x,dy,2)
      call stroke
   end do
   do iy=1,ny*10-1
      y=real(iy)/real(ny*10)*2.0-1.0
      dx=1.0
      if(iy/10*10==iy)then
         call setgray(0.5)
      else
         call setgray(0.8)
      end if
      call plot(0.0,y,3)
      call plot(dx,y,2)
      call stroke
   end do
   call setgray(0.0)
   call textx(0.75,0.0,'x')
   call textx(0.05,0.02,'0')
   call textx(0.55,0.02,'0.5')
   call textx(0.95,0.02,'1')
   call texty(-0.01,0.5,'y')
   call texty(0.0,-1.0,'-1')
   call texty(0.0,0.0,'0')
   call texty(0.0,1.0,'1')
   return
   end