def drdlat(r, lon, lat):
    """
    Compute the Jacobian of the transformation from latitudinal to
    rectangular coordinates.

    http://naif.jpl.nasa.gov/pub/naif/toolkit_docs/C/cspice/drdlat_c.html

    :param r: Distance of a point from the origin.
    :type r: float
    :param lon: Angle of the point from the XZ plane in radians.
    :type lon: float
    :param lat: Angle of the point from the XY plane in radians.
    :type lat: float
    :return: Matrix of partial derivatives.
    :rtype: 3x3-Element Array of floats
    """
    r = ctypes.c_double(r)
    lon = ctypes.c_double(lon)
    lat = ctypes.c_double(lat)
    jacobi = stypes.emptyDoubleMatrix()
    libspice.drdlat_c(r, lon, lat, jacobi)
    return stypes.cMatrixToNumpy(jacobi)