docs: def main():
      """
      NAME
          di_rot.py
  
      DESCRIPTION
          rotates set of directions to new coordinate system
  
      SYNTAX
          di_rot.py [command line options]
  
      OPTIONS
          -h prints help message and quits
          -f specify input file, default is standard input
          -F specify output file, default is standard output
          -D D specify  Dec of new coordinate system, default is 0
          -I I specify  Inc of new coordinate system, default is 90
      INTPUT/OUTPUT
          dec  inc   [space delimited]  
  
  
      """
      D,I=0.,90.
      outfile=""
      infile=""
      if '-h' in sys.argv:
          print(main.__doc__)
          sys.exit()
      if '-f' in sys.argv:
          ind=sys.argv.index('-f')
          infile=sys.argv[ind+1]
          data=numpy.loadtxt(infile)
      else:
          data=numpy.loadtxt(sys.stdin,dtype=numpy.float)
      if '-F' in sys.argv:
          ind=sys.argv.index('-F')
          outfile=sys.argv[ind+1]
          out=open(outfile,'w')
      if '-D' in sys.argv:
          ind=sys.argv.index('-D')
          D=float(sys.argv[ind+1])
      if '-I' in sys.argv:
          ind=sys.argv.index('-I')
          I=float(sys.argv[ind+1])
      if len(data.shape)>1: # 2-D array
          N=data.shape[0] 
          DipDir,Dip=numpy.ones(N,dtype=numpy.float).transpose()*(D-180.),numpy.ones(N,dtype=numpy.float).transpose()*(90.-I)
          data=data.transpose()
          data=numpy.array([data[0],data[1],DipDir ,Dip]).transpose()
          drot,irot=pmag.dotilt_V(data)
          drot=(drot-180.)%360.  # 
          for k in range(N): 
               if outfile=="":
                  print('%7.1f %7.1f ' % (drot[k],irot[k]))
               else:
                  out.write('%7.1f %7.1f\n' % (drot[k],irot[k]))
      else: 
          d,i=pmag.dotilt(data[0],data[1],(D-180.),90.-I)
          if outfile=="":
              print('%7.1f %7.1f ' % ((d-180.)%360.,i))
          else:
              out.write('%7.1f %7.1f\n' % ((d-180.)%360.,i))