T3Variations.unit
=================

.. py:method:: t3toolbox.frame_variations_format.T3Variations.unit(variation_shapes, index, stack_shape = (), use_jax = False)
   :staticmethod:


   .. code-block:: python

      def unit(
              variation_shapes,                                       # (tucker_variation_shapes, tt_variation_shapes)
              index:          typ.Tuple[bool, int, typ.Sequence[int]],  # (use_tt_coordinate, i, within_index)
              stack_shape:    typ.Tuple[int, ...] = (),               # full leading stack K + C
              use_jax:        bool = False,
      ) -> 'T3Variations':


   Canonical unit variation: zero except a single core entry set to 1.

   ``index = (use_tt_coordinate, i, within_index)`` selects the core (a tt-variation if
   ``use_tt_coordinate`` else a tucker-variation), its position ``i``, and the within-core index.
   These units are the standard basis of the variation cores -- an **overcomplete, non-ambient-
   orthogonal** generating set of the tangent space, not an orthonormal basis.