Subtract arguments, element-wise.
| Parameters : | x1, x2 : array_like 
  | 
|---|---|
| Returns : | y : ndarray 
  | 
Notes
Equivalent to x1 - x2 in terms of array broadcasting.
Examples
>>> np.subtract(1.0, 4.0)
-3.0
>>> x1 = np.arange(9.0).reshape((3, 3))
>>> x2 = np.arange(3.0)
>>> np.subtract(x1, x2)
array([[ 0.,  0.,  0.],
       [ 3.,  3.,  3.],
       [ 6.,  6.,  6.]])