pingouin.circ_vtest

pingouin.circ_vtest(angles, dir=0.0, w=None, d=None)

V test for non-uniformity of circular data with a specified mean direction.

Parameters:

angles1-D array_like

Samples of angles in radians. The range of angles must be either \([0, 2\pi]\) or \([-\pi, \pi]\). If angles is not expressed in radians (e.g. degrees or 24-hours), please use the pingouin.convert_angles() function prior to using the present function.

dirfloat

Suspected mean direction (angle in radians).

warray_like

Number of incidences per bins (i.e. “weights”), in case of binned angle data.

dfloat

Spacing (in radians) of bin centers for binned data. If supplied, a correction factor is used to correct for bias in the estimation of r.

Returns:

Vfloat

V-statistic

pvalfloat

P-value

Notes

H0: the population is uniformly distributed around the circle. HA: the population is not distributed uniformly around the circle but has a mean of dir.

Note: Not rejecting H0 may mean that the population is uniformly distributed around the circle OR that it has a mode but that this mode is not centered at dir.

The V test has more power than the Rayleigh test and is preferred if there is reason to believe in a specific mean direction.

Adapted from the Matlab Circular Statistics Toolbox.

Examples

1. V-test for non-uniformity of circular data.

>>> from pingouin import circ_vtest
>>> x = [0.785, 1.570, 3.141, 0.839, 5.934]
>>> v, pval = circ_vtest(x, dir=1)
>>> print(round(v, 3), pval)
2.486 0.05794648732225438

2. Specifying w and d

>>> v, pval = circ_vtest(x, dir=0.5, w=[.1, .2, .3, .4, .5], d=0.2)
>>> print(round(v, 3), round(pval, 5))
0.637 0.23086