T3Variations.stack
==================

.. py:method:: t3toolbox.frame_variations_format.T3Variations.stack(xx)
   :staticmethod:


   .. code-block:: python

      def stack(
              xx, # Array-like tree of T3Variations
      ):


   Stack array-like tree of T3Variations into a single T3Variation.

   .. rubric:: Examples

   >>> import numpy as np
   >>> import t3toolbox.frame_variations_format as bvf
   >>> import t3toolbox.corewise as cw
   >>> np.random.seed(0)
   >>> rnd = lambda x: np.random.randn(*x)
   >>> ss = (2, 3)                                   # stack
   >>> NN, nnU, nnD, rrL, rrR = (10, 11, 12), (8, 7, 8), (6, 7, 8), (2, 3, 4, 3), (5, 4, 6, 1)
   >>> tucker_variations = tuple(rnd(ss+(n, N)) for n, N in zip(nnD, NN))
   >>> tt_variations = tuple(rnd(ss+(rL, n, rR)) for rL, n, rR in zip(rrL[:-1], nnU, rrR[1:]))
   >>> V = bvf.T3Variations(tucker_variations, tt_variations)
   >>> V2 = bvf.T3Variations.stack(V.unstack())      # stack is the inverse of unstack
   >>> print(np.allclose(cw.corewise_norm(cw.corewise_sub(V.data, V2.data)), 0.0))
   True