tangentspace.py 文件源码

def tangent_space(covmats, Cref):
    """Project a set of covariance matrices in the tangent space according to the given reference point Cref

    :param covmats: Covariance matrices set, Ntrials X Nchannels X Nchannels
    :param Cref: The reference covariance matrix
    :returns: the Tangent space , a matrix of Ntrials X (Nchannels*(Nchannels+1)/2)

    """
    Nt, Ne, Ne = covmats.shape
    Cm12 = invsqrtm(Cref)
    idx = numpy.triu_indices_from(Cref)
    T = numpy.empty((Nt, Ne * (Ne + 1) / 2))
    coeffs = (
        numpy.sqrt(2) *
        numpy.triu(
            numpy.ones(
                (Ne,
                 Ne)),
            1) +
        numpy.eye(Ne))[idx]
    for index in range(Nt):
        tmp = numpy.dot(numpy.dot(Cm12, covmats[index, :, :]), Cm12)
        tmp = logm(tmp)
        T[index, :] = numpy.multiply(coeffs, tmp[idx])
    return T