Stack arrays in sequence vertically (row wise).
Take a sequence of arrays and stack them vertically to make a single array. Rebuild arrays divided by vsplit.
Parameters :  tup : sequence of ndarrays


Returns :  stacked : ndarray

See also
Notes
The function is applied to both the _data and the _mask, if any.
Examples
>>> a = np.array([1, 2, 3])
>>> b = np.array([2, 3, 4])
>>> np.vstack((a,b))
array([[1, 2, 3],
[2, 3, 4]])
>>> a = np.array([[1], [2], [3]])
>>> b = np.array([[2], [3], [4]])
>>> np.vstack((a,b))
array([[1],
[2],
[3],
[2],
[3],
[4]])