The Mandelbrot distribution

Calculate and plot (BOX option) the Mandelbrot distribution

1     FUN2 10 mandel.f [1] -2.4 .8 [1] -1.2 1.2 ' '                                            
2     HI/PL 10 BOX                                                                             

FORTRAN Routine MANDEL

      real function mandel(xp)
3     dimension xp(2)                                                                          
      data nmax/30/
      x=xp(1)
      y=xp(2)
      xx=0.
      yy=0.
      do n=1,nmax
         tt=xx*xx-yy*yy+x
         yy=2.*xx*yy+y
         xx=tt
         if (4..lt.xx*xx+yy*yy) go to 20
      enddo
   20 mandel=float(n)/float(nmax)
      end
  1. This example shows one of the usages of COMIS. In this case, the name of the function to be plotted by FUN2 is replaced by a COMIS FORTRAN function.
  2. CHOPT=' ' in the command FUN2 means to fill only the histogram without producing the plot which is by default a surface. The plot is produced by the command HIST/PLOT .
  3. The vector XP is an input parameter given by FUN2 , for each cell, to the FORTRAN program. XP contains the X and Y coordinates of each cell. You can try to insert: 
          print*, XP
    in mandel.f to see the values changing (in this case it is better to set the input parameter of the macro to 10).

PAW TutorialLast update: 1999/04/01 14.57
Olivier.Couet@Cern.Ch