docs: def draw_zijderveld(self):
          """
          Draws the zijderveld plot in the GUI on canvas1
          """
          self.fig1.clf()
          axis_bounds = [0, .1, 1, .85]
          self.zijplot = self.fig1.add_axes(
              axis_bounds, frameon=False, facecolor='None', label='zig_orig', zorder=0)
          self.zijplot.clear()
          self.zijplot.axis('equal')
          self.zijplot.xaxis.set_visible(False)
          self.zijplot.yaxis.set_visible(False)
  
          self.MS = 6*self.GUI_RESOLUTION
          self.dec_MEC = 'k'
          self.dec_MFC = 'r'
          self.inc_MEC = 'k'
          self.inc_MFC = 'b'
          self.MS = 6*self.GUI_RESOLUTION
          self.zijdblock_steps = self.Data[self.s]['zijdblock_steps']
          self.vds = self.Data[self.s]['vds']
  
          self.zijplot.plot(self.CART_rot_good[:, 0], -1*self.CART_rot_good[:, 1], 'ro-',
                            markersize=self.MS, clip_on=False, picker=True, zorder=1)  # x,y or N,E
          self.zijplot.plot(self.CART_rot_good[:, 0], -1*self.CART_rot_good[:, 2], 'bs-',
                            markersize=self.MS, clip_on=False, picker=True, zorder=1)  # x-z or N,D
  
          for i in range(len(self.CART_rot_bad)):
              self.zijplot.plot(self.CART_rot_bad[:, 0][i], -1 * self.CART_rot_bad[:, 1][i], 'o', mfc='None',
                                mec=self.dec_MEC, markersize=self.MS, clip_on=False, picker=False)  # x,y or N,E
              self.zijplot.plot(self.CART_rot_bad[:, 0][i], -1 * self.CART_rot_bad[:, 2][i], 's', mfc='None',
                                mec=self.inc_MEC, markersize=self.MS, clip_on=False, picker=False)  # x-z or N,D
  
          if self.preferences['show_Zij_treatments']:
              for i in range(len(self.zijdblock_steps)):
                  if int(self.preferences['show_Zij_treatments_steps']) != 1:
                      if i != 0 and (i+1) % int(self.preferences['show_Zij_treatments_steps']) == 0:
                          self.zijplot.text(self.CART_rot[i][0], -1*self.CART_rot[i][2], "  %s" % (
                              self.zijdblock_steps[i]), fontsize=8*self.GUI_RESOLUTION, color='gray', ha='left', va='center')  # inc
                  else:
                      self.zijplot.text(self.CART_rot[i][0], -1*self.CART_rot[i][2], "  %s" % (
                          self.zijdblock_steps[i]), fontsize=10*self.GUI_RESOLUTION, color='gray', ha='left', va='center')  # inc
  
          # -----
  
          xmin, xmax = self.zijplot.get_xlim()
          if xmax < 0:
              xmax = 0
          if xmin > 0:
              xmin = 0
          # else:
          #    xmin=xmin+xmin%0.2
  
          props = dict(color='black', linewidth=1.0, markeredgewidth=0.5)
  
          xlocs = array(list(arange(0.2, xmax, 0.2)) +
                        list(arange(-0.2, xmin, -0.2)))
          if len(xlocs) > 0:
              xtickline, = self.zijplot.plot(
                  xlocs, [0]*len(xlocs), linestyle='', marker='+', **props)
              xtickline.set_clip_on(False)
  
          axxline, = self.zijplot.plot([xmin, xmax], [0, 0], **props)
          axxline.set_clip_on(False)
  
          TEXT = ""
          if self.COORDINATE_SYSTEM == 'specimen':
              self.zijplot.text(xmax, 0, ' x', fontsize=10,
                                verticalalignment='bottom')
          else:
              if self.ORTHO_PLOT_TYPE == 'N-S':
                  TEXT = " N"
              elif self.ORTHO_PLOT_TYPE == 'E-W':
                  TEXT = " E"
              else:
                  TEXT = " x"
              self.zijplot.text(xmax, 0, TEXT, fontsize=10,
                                verticalalignment='bottom')
  
          # -----
  
          ymin, ymax = self.zijplot.get_ylim()
          if ymax < 0:
              ymax = 0
          if ymin > 0:
              ymin = 0
  
          ylocs = array(list(arange(0.2, ymax, 0.2)) +
                        list(arange(-0.2, ymin, -0.2)))
          if len(ylocs) > 0:
              ytickline, = self.zijplot.plot(
                  [0]*len(ylocs), ylocs, linestyle='', marker='+', **props)
              ytickline.set_clip_on(False)
  
          axyline, = self.zijplot.plot([0, 0], [ymin, ymax], **props)
          axyline.set_clip_on(False)
  
          TEXT1, TEXT2 = "", ""
          if self.COORDINATE_SYSTEM == 'specimen':
              TEXT1, TEXT2 = " y", "      z"
          else:
              if self.ORTHO_PLOT_TYPE == 'N-S':
                  TEXT1, TEXT2 = " E", "     D"
              elif self.ORTHO_PLOT_TYPE == 'E-W':
                  TEXT1, TEXT2 = " S", "     D"
              else:
                  TEXT1, TEXT2 = " y", "      z"
          self.zijplot.text(0, ymin, TEXT1, fontsize=10,
                            color='r', verticalalignment='top')
          self.zijplot.text(0, ymin, '    ,', fontsize=10,
                            color='k', verticalalignment='top')
          self.zijplot.text(0, ymin, TEXT2, fontsize=10,
                            color='b', verticalalignment='top')
  
          # ----
  
          if self.ORTHO_PLOT_TYPE == 'N-S':
              STRING = ""
              #STRING1="N-S orthogonal plot"
              self.fig1.text(0.01, 0.98, "Zijderveld plot: x = North", {
                             'family': self.font_type, 'fontsize': 10*self.GUI_RESOLUTION, 'style': 'normal', 'va': 'center', 'ha': 'left'})
          elif self.ORTHO_PLOT_TYPE == 'E-W':
              STRING = ""
              #STRING1="E-W orthogonal plot"
              self.fig1.text(0.01, 0.98, "Zijderveld plot:: x = East", {
                             'family': self.font_type, 'fontsize': 10*self.GUI_RESOLUTION, 'style': 'normal', 'va': 'center', 'ha': 'left'})
  
          elif self.ORTHO_PLOT_TYPE == 'PCA_dec':
              self.fig1.text(0.01, 0.98, "Zijderveld plot", {
                             'family': self.font_type, 'fontsize': 10*self.GUI_RESOLUTION, 'style': 'normal', 'va': 'center', 'ha': 'left'})
              if 'specimen_dec' in list(self.current_fit.pars.keys()) and type(self.current_fit.pars['specimen_dec']) != str:
                  STRING = "X-axis rotated to best fit line declination (%.0f); " % (
                      self.current_fit.pars['specimen_dec'])
              else:
                  STRING = "X-axis rotated to NRM (%.0f); " % (
                      self.zijblock[0][1])
          else:
              self.fig1.text(0.01, 0.98, "Zijderveld plot", {
                             'family': self.font_type, 'fontsize': 10*self.GUI_RESOLUTION, 'style': 'normal', 'va': 'center', 'ha': 'left'})
              STRING = "X-axis rotated to NRM (%.0f); " % (self.zijblock[0][1])
              #STRING1="Zijderveld plot"
  
          STRING = STRING+"NRM=%.2e " % (self.zijblock[0][3]) + 'Am^2'
          self.fig1.text(0.01, 0.95, STRING, {'family': self.font_type, 'fontsize': 8 *
                                              self.GUI_RESOLUTION, 'style': 'normal', 'va': 'center', 'ha': 'left'})
  
          xmin, xmax = self.zijplot.get_xlim()
          ymin, ymax = self.zijplot.get_ylim()
  
          self.zij_xlim_initial = (xmin, xmax)
          self.zij_ylim_initial = (ymin, ymax)
  
          self.canvas1.draw()