C     Plotting program for general purpose using postscript
      call init
      call viewport(0.2,0.2,0.8,0.8)
      call xyworld(-0.2,-0.2,1.2,1.2)
      call line(0.5, 0.0, 0.5, 0.02, 0.0, 2.0, 1)
      call line(1.0, 0.0, 1.0, 0.02, 0.0, 2.0,1)
      call line(0.0, 0.5, 0.02, 0.5, 0.0, 2.0,1)
      call line(0.0, 1.0, 0.02, 1.0, 0.0, 2.0,1)
      call arrow(-0.1, 0.0, 1.2, 0.0, 0.02, 0.0, 2.0)
      call arrow(0.0, -0.1, 0.0, 1.2, 0.02, 0.0, 2.0)
      call textx(1.2,-0.02,1,'x')
      call textx(0.5,-0.02,3,'0.5')
      call textx(1.0,-0.02,3,'1.0')
      call texty(-0.02,1.2,1,'y')
      call texty(0.0,0.5,3,'0.5')
      call texty(0.0,1.0,3,'1.0')
      call textx(-0.06,-0.02,1,'O')
      call plotd1
      call fin
      stop
      end
c
      subroutine plotd1
      common /ndata/n,nx,ny,ns
      common /xydata/x(100),y(100)
c     call clip(-1.0,-1.0,1.0,1.0)
      write(1,*) ' 1.0 setlinewidth'
      write(1,*) ' 0.6 setgray'
      call linety(1)
      m=10
      do 50 ix=0,m
      do 50 iy=0,m
       x0=0.0+1.0*float(ix)/float(m)
       y0=0.0+1.0*float(iy)/float(m)
       dt=0.05
       dx=1.0
       dy=3.0*x0*y0
       ds=sqrt(dx**2+dy**2)
       if(ds.ne.0.0) then
       x1=x0+dx/ds*0.05
       y1=y0+dy/ds*0.05
       call arrow(x0,y0,x1,y1,0.01,0.6,1.0)
       end if
   50 continue
      write(1,*) ' stroke '
      write(1,*) ' newpath'
      write(1,*) ' 0.4 setgray'
      write(1,*) ' 1.2 setlinewidth'
      call linety(1)
      n=40
      m=1
      do 10 ix=0,0
      do 10 iy=0,0
       x(0)=0.0
       y(0)=0.1
c      write(*,*) c1,c2
       dt=0.0128
       call plot(x(0),y(0),3)
        do 20 it=1,2*n
        x(it)= x(it-1)+(1.0)*(dt)
        y(it)= y(it-1)+(3.0*x(it-1)*y(it-1))*(dt)
        call plot(x(it),y(it),2)
   20 continue
c       write(1,*) ' stroke '
   10 continue
      return
      end