colour.algebra.eigen_decomposition#

colour.algebra.eigen_decomposition(a: ArrayLike, eigen_w_v_count: int | None = None, descending_order: bool = True, covariance_matrix: bool = False) → Tuple[NDArrayFloat, NDArrayFloat][source]#

Return the eigen-values \(w\) and eigen-vectors \(v\) of given array \(a\) in given order.

Parameters:

  • a (ArrayLike) – Array to return the eigen-values \(w\) and eigen-vectors \(v\) for

  • eigen_w_v_count (int | None) – Eigen-values \(w\) and eigen-vectors \(v\) count.

  • descending_order (bool) – Whether to return the eigen-values \(w\) and eigen-vectors \(v\) in descending order.

  • covariance_matrix (bool) – Whether to compute the eigen-values \(w\) and eigen-vectors \(v\) of the array \(a\) covariance matrix \(A =a^T\cdot a\).

Returns:

Tuple of eigen-values \(w\) and eigen-vectors \(v\). The eigenv-alues are in given order, each repeated according to its multiplicity. The column v[:, i] is the normalized eigen-vector corresponding to the eige-nvalue w[i].

Return type:

tuple

Examples

>>> a = np.diag([1, 2, 3])
>>> w, v = eigen_decomposition(a)
>>> w
array([ 3.,  2.,  1.])
>>> v
array([[ 0.,  0.,  1.],
       [ 0.,  1.,  0.],
       [ 1.,  0.,  0.]])
>>> w, v = eigen_decomposition(a, 1)
>>> w
array([ 3.])
>>> v
array([[ 0.],
       [ 0.],
       [ 1.]])
>>> w, v = eigen_decomposition(a, descending_order=False)
>>> w
array([ 1.,  2.,  3.])
>>> v
array([[ 1.,  0.,  0.],
       [ 0.,  1.,  0.],
       [ 0.,  0.,  1.]])
>>> w, v = eigen_decomposition(a, covariance_matrix=True)
>>> w
array([ 9.,  4.,  1.])
>>> v
array([[ 0.,  0.,  1.],
       [ 0.,  1.,  0.],
       [ 1.,  0.,  0.]])