code: def firstSacDist(fm):
        
      ang, leng, ad, ld = anglendiff(fm, return_abs=True)
      y_arg = leng[0][np.roll(fm.fix == min(fm.fix), 1)]/fm.pixels_per_degree
      x_arg = reshift(ang[0][np.roll(fm.fix == min(fm.fix), 1)])
      bins = [list(range(int(ceil(np.nanmax(y_arg)))+1)), np.linspace(-180, 180, 361)]
      return makeHist(x_arg, y_arg, fit=None, bins = bins)
docs: Computes the distribution of angle and length
          combinations that were made as first saccades
          
          Parameters:
              fm : ocupy.fixmat 
                  The fixation data to be analysed