operations.py 文件源码

def sum_visibility(vis: Visibility, direction: SkyCoord) -> numpy.array:
    """ Direct Fourier summation in a given direction

    :param vis: Visibility to be summed
    :param direction: Direction of summation
    :return: flux[nch,npol], weight[nch,pol]
    """
    # TODO: Convert to Visibility or remove?

    assert isinstance(vis, Visibility) or isinstance(vis, BlockVisibility), vis

    svis = copy_visibility(vis)

    l, m, n = skycoord_to_lmn(direction, svis.phasecentre)
    phasor = numpy.conjugate(simulate_point(svis.uvw, l, m))

    # Need to put correct mapping here
    _, frequency = get_frequency_map(svis, None)

    frequency = list(frequency)

    nchan = max(frequency) + 1
    npol = svis.polarisation_frame.npol

    flux = numpy.zeros([nchan, npol])
    weight = numpy.zeros([nchan, npol])

    coords = svis.vis, svis.weight, phasor, list(frequency)
    for v, wt, p, ic in zip(*coords):
        for pol in range(npol):
            flux[ic, pol] += numpy.real(wt[pol] * v[pol] * p)
            weight[ic, pol] += wt[pol]

    flux[weight > 0.0] = flux[weight > 0.0] / weight[weight > 0.0]
    flux[weight <= 0.0] = 0.0
    return flux, weight