eelbrain.testnd.Vector

class eelbrain.testnd.Vector(y, match=None, sub=None, data=None, samples=10000, tmin=None, tfce=False, tstart=None, tstop=None, parc=None, force_permutation=False, norm=False, **criteria)

Test a vector field for vectors with non-random direction

Parameters

  • y (NDVar) – Dependent variable (needs to include one vector dimension).

  • match (None | categorial) – Combine data for these categories before testing.

  • sub (index) – Perform test with a subset of the data.

  • data (Dataset) – If a Dataset is specified, all data-objects can be specified as names of Dataset variables

  • samples (int) – Number of samples for permutation test (default 10000).

  • tmin (scalar) – Threshold value for forming clusters.

  • tfce (bool | scalar) – Use threshold-free cluster enhancement. Use a scalar to specify the step of TFCE levels (for tfce is True, 0.1 is used).

  • tstart (scalar) – Start of the time window for the permutation test (default is the beginning of y).

  • tstop (scalar) – Stop of the time window for the permutation test (default is the end of y).

  • parc (str) – Collect permutation statistics for all regions of the parcellation of this dimension. For threshold-based test, the regions are disconnected.

  • force_permutation (bool) – Conduct permutations regardless of whether there are any clusters.

  • norm (bool) – Use the vector norm as univariate test statistic (instead of Hotelling’s T-Square statistic).

  • mintime (scalar) – Minimum duration for clusters (in seconds).

  • minsource (int) – Minimum number of sources per cluster.

Variables

  • n (int) – Number of cases.

  • difference (NDVar) – The vector field averaged across cases.

  • t2 (NDVar | None) – Hotelling T-Square map; None if the test used norm=True.

  • p (NDVar | None) – Map of p-values corrected for multiple comparison (or None if no correction was performed).

  • tfce_map (NDVar | None) – Map of the test statistic processed with the threshold-free cluster enhancement algorithm (or None if no TFCE was performed).

  • clusters (None | Dataset) – For cluster-based tests, a table of all clusters. Otherwise a table of all significant regions (or None if permutations were omitted). See also the find_clusters() method.

See also

testnd

Information on the different permutation methods

Notes

Vector tests are based on the Hotelling T-Square statistic. Computation of the T-Square statistic relies on 1.

References

1

Kopp, J. (2008). Efficient numerical diagonalization of hermitian 3 x 3 matrices. International Journal of Modern Physics C, 19(3), 523-548. 10.1142/S0129183108012303

Methods

cluster(cluster_id)

Retrieve a specific cluster as NDVar

compute_probability_map(**sub)

Compute a probability map

find_clusters([pmin, maps])

Find significant regions or clusters

find_peaks()

Find peaks in a threshold-free cluster distribution

info_list([computation])

List with information about the test

masked_difference([p, name])

Difference map masked by significance

masked_parameter_map([pmin])

Statistical parameter map masked by significance