docs: def plot_prof_sparse(self, mod, species, xlim1, xlim2, ylim1, ylim2,
                           sparse, symbol):
  
          """
          plot one species for cycle between xlim1 and xlim2.
  
          Parameters
          ----------
          species : list
              which species to plot.
          mod : string or integer
              Model (cycle) to plot.
          xlim1, xlim2 : float
              Mass coordinate range.
          ylim1, ylim2 : float
              Mass fraction coordinate range.
          sparse : integer
              Sparsity factor for points.
          symbol : string
              which symbol you want to use?
  
          """
          mass=self.se.get(mod,'mass')
          Xspecies=self.se.get(mod,'yps',species)
          pyl.plot(mass[0:len(mass):sparse],np.log10(Xspecies[0:len(Xspecies):sparse]),symbol)
          pyl.xlim(xlim1,xlim2)
          pyl.ylim(ylim1,ylim2)
          pyl.legend()