code: def dovds(data):
      
      vds, X = 0, []
      for rec in data:
          X.append(dir2cart(rec))
      for k in range(len(X) - 1):
          xdif = X[k + 1][0] - X[k][0]
          ydif = X[k + 1][1] - X[k][1]
          zdif = X[k + 1][2] - X[k][2]
          vds += np.sqrt(xdif**2 + ydif**2 + zdif**2)
      vds += np.sqrt(X[-1][0]**2 + X[-1][1]**2 + X[-1][2]**2)
      return vds
docs: calculates vector difference sum for demagnetization data