code: def plot_delta_m(fignum, B, DM, Bcr, s):
      
      plt.figure(num=fignum)
      plt.clf()
      if not isServer:
          plt.figtext(.02, .01, version_num)
      plt.plot(B, DM, 'b')
      plt.xlabel('B (T)')
      plt.ylabel('Delta M')
      linex = [0, Bcr, Bcr]
      liney = [old_div(DM[0], 2.), old_div(DM[0], 2.), 0]
      plt.plot(linex, liney, 'r')
      plt.title(s)
docs: function to plot Delta M curves
  
      Parameters
      __________
      fignum : matplotlib figure number
      B : array of field values
      DM : array of difference between top and bottom curves in hysteresis loop
      Bcr : coercivity of remanence
      s : specimen name