Optimize the index computation

[mchalela]

GriSPy/grispy/core.py

Lines 350 to 354 in e70b75c

	def _digitize(self, data, bins):
	"""Return data bin index."""
	N = len(bins) - 1
	d = (N * (data - bins[0]) / (bins[-1] - bins[0])).astype(np.int)
	return d

This is a faster way of computing the index:

 def _digitize(self, data, bins): 
     """Return data bin index.""" 
     # allowed indeces with int16: (-32768 to 32767)
     d = ((data - bins[0]) / (bins[1] - bins[0])).astype(np.int16)
     return d