operations.py 文件源码

def remove_continuum_blockvisibility(vis: BlockVisibility, degree=1, mask=None) -> BlockVisibility:
    """ Fit and remove continuum visibility

    Fit a polynomial in frequency of the specified degree where mask is True

    :param vis:
    :param degree: Degree of polynomial
    :param mask:
    :return:
    """
    assert isinstance(vis, Visibility) or isinstance(vis, BlockVisibility), vis

    if mask is not None:
        assert numpy.sum(mask) > 2 * degree, "Insufficient channels for fit"

    nchan = len(vis.frequency)
    x = (vis.frequency - vis.frequency[nchan // 2]) / (vis.frequency[0] - vis.frequency[nchan // 2])
    for row in range(vis.nvis):
        for ant2 in range(vis.nants):
            for ant1 in range(vis.nants):
                for pol in range(vis.polarisation_frame.npol):
                    wt = numpy.sqrt(vis.data['weight'][row, ant2, ant1, :, pol])
                    if mask is not None:
                        wt[mask] = 0.0
                    fit = numpy.polyfit(x, vis.data['vis'][row, ant2, ant1, :, pol], w=wt, deg=degree)
                    prediction = numpy.polyval(fit, x)
                    vis.data['vis'][row, ant2, ant1, :, pol] -= prediction
    return vis