docs: def plot_b(Figs, araiblock, zijdblock, pars):
      """
      deprecated (used in thellier_magic/microwave_magic)
      """
      angle = zijdblock[0][1]
      plotblock = []
      Dir, zx, zy, zz, ax, ay = [], [], [], [], [], []
      zstart, zend = 0, len(zijdblock)
      first_Z, first_I = araiblock[0], araiblock[1]
      for rec in zijdblock:
          if rec[0] == pars["measurement_step_min"]:
              Dir.append((rec[1] - angle, rec[2],
                          old_div(rec[3], zijdblock[0][3])))
          if rec[0] == pars["measurement_step_max"]:
              Dir.append((rec[1] - angle, rec[2],
                          old_div(rec[3], zijdblock[0][3])))
      for drec in Dir:
          cart = pmag.dir2cart(drec)
          zx.append(cart[0])
        #   zy.append(-cart[1])
        #   zz.append(-cart[2])
          zy.append(cart[1])
          zz.append(cart[2])
      if len(zx) > 0:
          plt.figure(num=Figs['zijd'])
          plt.scatter(zx, zy, marker='d', s=100, c='y')
          plt.scatter(zx, zz, marker='d', s=100, c='y')
          plt.axis("equal")
      ax.append(old_div(first_I[0][3], first_Z[0][3]))
      ax.append(old_div(first_I[-1][3], first_Z[0][3]))
      ay.append(old_div(first_Z[0][3], first_Z[0][3]))
      ay.append(old_div(first_Z[-1][3], first_Z[0][3]))
      for k in range(len(first_Z)):
          if first_Z[k][0] == pars["measurement_step_min"]:
              ay[0] = (old_div(first_Z[k][3], first_Z[0][3]))
          if first_Z[k][0] == pars["measurement_step_max"]:
              ay[1] = (old_div(first_Z[k][3], first_Z[0][3]))
          if first_I[k][0] == pars["measurement_step_min"]:
              ax[0] = (old_div(first_I[k][3], first_Z[0][3]))
          if first_I[k][0] == pars["measurement_step_max"]:
              ax[1] = (old_div(first_I[k][3], first_Z[0][3]))
      new_Z, new_I = [], []
      for zrec in first_Z:
          if zrec[0] >= pars['measurement_step_min'] and zrec[0] <= pars['measurement_step_max']:
              new_Z.append(zrec)
      for irec in first_I:
          if irec[0] >= pars['measurement_step_min'] and irec[0] <= pars['measurement_step_max']:
              new_I.append(irec)
      newblock = [new_Z, new_I]
      plot_teq(Figs['eqarea'], newblock, "", pars)
      plt.figure(num=Figs['arai'])
      plt.scatter(ax, ay, marker='d', s=100, c='y')
  #
  #  find midpoint between two endpoints
  #
      sy = []
      sy.append((pars["specimen_b"] * ax[0] +
                 old_div(pars["specimen_ytot"], first_Z[0][3])))
      sy.append((pars["specimen_b"] * ax[1] +
                 old_div(pars["specimen_ytot"], first_Z[0][3])))
      plt.plot(ax, sy, 'g', linewidth=2)
      bounds = plt.axis()
      if pars['specimen_grade'] != '':
          notestr = 'Grade: ' + pars["specimen_grade"]
          plt.text(.7 * bounds[1], .9 * bounds[3], notestr)
      notestr = 'B: ' + '%6.2f' % (pars["specimen_int"] * 1e6) + ' uT'
      plt.text(.7 * bounds[1], .8 * bounds[3], notestr)