docs: def linestylecb(i,a=5,b=3):
      '''
          version of linestyle function with colourblind colour scheme
  
          returns linetyle, marker, color (see example)
  
          Parameters
          ----------
          i : integer
          Number of linestyle combination - there are many....
          a : integer
          Spacing of marks.  The default is 5.
          b : integer
          Modulation in case of plotting many nearby lines.  The default
          is 3.
  
          Examples
          --------
  
          >>> plot(x,sin(x),ls=linestyle(7)[0], marker=linestyle(7)[1], \
                   color=linestyle(7)[2],markevery=linestyle(7)[3])
  
  
          (c) 2014 FH
          '''
  
      lines=['-','--','-.',':']
      points=['v','^','<','>','1','2','3','4','s','p','*','h','H','+','x','D','d','o']
      colors=['b','g','r','c','m','k']
      col=colourblind(i)
      style=lines[sc.mod(i,4)]
      point=points[sc.mod(i,18)]
      mark_i    = a+sc.mod(i,b)
      return style,point,col,mark_i