docs: def plot_day(fignum, BcrBc, S, sym, **kwargs):
      """
      function to plot Day plots
  
      Parameters
      _________
      fignum : matplotlib figure number
      BcrBc : list or array ratio of coercivity of remenance to coercivity
      S : list or array ratio of saturation remanence to saturation magnetization (squareness)
      sym : matplotlib symbol (e.g., 'rs' for red squares)
      **kwargs :  dictionary with {'names':[list of names for symbols]}
      """
      plt.figure(num=fignum)
      plt.plot(BcrBc, S, sym)
      plt.axhline(0, color='k')
      plt.axhline(.05, color='k')
      plt.axhline(.5, color='k')
      plt.axvline(1, color='k')
      plt.axvline(4, color='k')
      plt.xlabel('Bcr/Bc')
      plt.ylabel('Mr/Ms')
      plt.title('Day Plot')
      plt.xlim(0, 6)
      #bounds= plt.axis()
      #plt.axis([0, bounds[1],0, 1])
      mu_o = 4. * np.pi * 1e-7
      Bc_sd = 46e-3  # (MV1H) dunlop and carter-stiglitz 2006 (in T)
      Bc_md = 5.56e-3  # (041183) dunlop and carter-stiglitz 2006 (in T)
      chi_sd = 5.20e6 * mu_o  # now in T
      chi_md = 4.14e6 * mu_o  # now in T
      chi_r_sd = 4.55e6 * mu_o  # now in T
      chi_r_md = 0.88e6 * mu_o  # now in T
      Bcr_sd, Bcr_md = 52.5e-3, 26.1e-3  # (MV1H and 041183 in DC06 in tesla)
      Ms = 480e3  # A/m
      p = .1  # from Dunlop 2002
      N = old_div(1., 3.)  # demagnetizing factor
      f_sd = np.arange(1., 0., -.01)  # fraction of sd
      f_md = 1. - f_sd  # fraction of md
      f_sp = 1. - f_sd  # fraction of sp
      # Mr/Ms ratios for USD,MD and Jax shaped
      sdrat, mdrat, cbrat = 0.498, 0.048, 0.6
      Mrat = f_sd * sdrat + f_md * mdrat  # linear mixing - eq. 9 in Dunlop 2002
      Bc = old_div((f_sd * chi_sd * Bc_sd + f_md * chi_md * Bc_md),
                   (f_sd * chi_sd + f_md * chi_md))  # eq. 10 in Dunlop 2002
      Bcr = old_div((f_sd * chi_r_sd * Bcr_sd + f_md * chi_r_md * Bcr_md),
                    (f_sd * chi_r_sd + f_md * chi_r_md))  # eq. 11 in Dunlop 2002
      chi_sps = np.arange(1, 5) * chi_sd
      plt.plot(old_div(Bcr, Bc), Mrat, 'r-')
      if 'names' in list(kwargs.keys()):
          names = kwargs['names']
          for k in range(len(names)):
              plt.text(BcrBc[k], S[k], names[k])