docs: def plot_ratio(cid, ax, plotman, title, alpha, vmin, vmax,
                 xmin, xmax, zmin, zmax, xunit, cbtiks, elecs):
      '''Plot ratio of two conductivity directions.
      '''
      # handle options
      cblabel = 'anisotropy ratio'
      zlabel = 'z [' + xunit + ']'
      xlabel = 'x [' + xunit + ']'
      # cm = 'brg'
      cm = 'RdYlGn'
      xmin, xmax, zmin, zmax, vmin, vmax = check_minmax(
              plotman,
              cid,
              xmin, xmax,
              zmin, zmax,
              vmin, vmax,
              )
      # plot
      fig, ax, cnorm, cmap, cb, scalarMap = plotman.plot_elements_to_ax(
              cid=cid,
              ax=ax,
              xmin=xmin,
              xmax=xmax,
              zmin=zmin,
              zmax=zmax,
              cblabel=cblabel,
              cbnrticks=cbtiks,
              title=title,
              zlabel=zlabel,
              xlabel=xlabel,
              plot_colorbar=True,
              cmap_name=cm,
              no_elecs=elecs,
              cbmin=vmin,
              cbmax=vmax,
              )
      return fig, ax, cnorm, cmap, cb