helios.py 文件源码

def _mag_ness_fromascii(probe, year, doy, try_download=True):
    """
    Read in a single day of 6 second magnetic field data.

    Data is read from orignal ascii files, and saved to a hdf file for faster
    access after the first read.

    Parameters
    ----------
    probe : int, string
        Helios probe to import data from. Must be 1 or 2.
    year : int
        Year
    doy : int
        Day of year

    Returns
    -------
    data : DataFrame
        6 second magnetic field data set
    """
    probe = _check_probe(probe)
    local_dir = _ness_localdir(probe, year)
    remote_url = ('ftp://spdf.sci.gsfc.nasa.gov/pub/data/helios/helios' +
                  probe + '/mag/6sec_ness/' + str(year) + '/')
    fname = _ness_fname(probe, year, doy) + '.asc'
    f = helper.load(fname, local_dir, remote_url, try_download=try_download)

    # Read in data
    headings = ['probe', 'year', 'doy', 'hour', 'minute', 'second', 'naverage',
                'Bx', 'By', 'Bz', '|B|', 'sigma_Bx', 'sigma_By', 'sigma_Bz']

    colspecs = [(1, 2), (2, 4), (4, 7), (7, 9), (9, 11), (11, 13), (13, 15),
                (15, 22), (22, 29), (29, 36), (36, 42), (42, 48), (48, 54),
                (54, 60)]
    data = pd.read_fwf(f, names=headings, header=None,
                       colspecs=colspecs)

    # Process data
    data['year'] += 1900
    # Convert date info to datetime
    data['Time'] = pd.to_datetime(data['year'], format='%Y') + \
        pd.to_timedelta(data['doy'] - 1, unit='d') + \
        pd.to_timedelta(data['hour'], unit='h') + \
        pd.to_timedelta(data['minute'], unit='m') + \
        pd.to_timedelta(data['second'], unit='s')
    data = data.drop(['year', 'doy', 'hour', 'minute', 'second'], axis=1)
    data = data.set_index('Time', drop=False)

    # Save data to a hdf store
    if use_hdf:
        _save_hdf(data, local_dir, _ness_fname(probe, year, doy))
    return(data)