Note
This page is a reference documentation. It only explains the function signature, and not how to use it. Please refer to the user guide for the big picture.
nilearn.connectome.vec_to_sym_matrix#
- nilearn.connectome.vec_to_sym_matrix(vec, diagonal=None)[source]#
Return the symmetric matrix given its flattened lower triangular part.
Acts on the last dimension of the array if not 1-dimensional. Diagonal can be encompassed in vec or given separately. In both cases, note that diagonal elements are multiplied by sqrt(2).
New in version 0.3.
- Parameters:
- vecnumpy.ndarray or list of numpy arrays, shape (…, n_columns * (n_columns + 1) /2) or
(…, (n_columns - 1) * n_columns / 2) if diagonal is given separately. The input array.
- diagonalnumpy.ndarray, shape (…, n_columns), optional
The diagonal array to be stacked to vec. If None, the diagonal is assumed to be included in vec.
- Returns:
- symnumpy.ndarray, shape (…, n_columns, n_columns).
The output symmetric matrix.
See also
Notes
This function is meant to be the inverse of sym_matrix_to_vec. If you have discarded the diagonal in sym_matrix_to_vec, you need to provide it separately to reconstruct the symmetric matrix. For instance this can be useful for correlation matrices for which we know the diagonal is 1.