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# Reading and Writing Time Series

## Built-in Readers

Since |TimeSeries| and |BinnedTimeSeries| are subclasses of |Table|, they have `read()` and `write()` methods that can be used to read and write time series from files. We include a few readers for well-defined formats in `astropy.timeseries`. For instance we have readers for light curves in FITS format from the Kepler and TESS missions.

### Example

In this demonstration of using Kepler FITS time series, we start off by fetching an example file:

    from astropy.utils.data import get_pkg_data_filename
    example_data = get_pkg_data_filename('timeseries/kplr010666592-2009131110544_slc.fits')

Note

The light curve provided here is handpicked for example purposes. To get other Kepler light curves for science purposes using Python, see the astroquery affiliated package.

This will set `example_data` to the filename of the downloaded file (so you can replace this by the filename for the file you want to read in). We can then read in the time series using:

    from astropy.timeseries import TimeSeries
    kepler = TimeSeries.read(example_data, format='kepler.fits', unit_parse_strict='silent')

Now we can check that the time series has been read in correctly:

    import matplotlib.pyplot as plt

    fig, ax = plt.subplots()
    ax.plot(kepler.time.jd, kepler['sap_flux'], 'k.', markersize=1)
    ax.set(xlabel='Julian Date', ylabel='SAP Flux (e-/s)')

## Reading Common Light Curve Formats

At the moment only a few formats are defined in `astropy` itself, in part because there are not many well-documented formats for storing time series. So in many cases, you will likely have to first read in your files using the more generic |Table| class (see Table Data). In fact, the `TimeSeries.read` and `BinnedTimeSeries.read` methods can do this behind the scenes. If the table cannot be read by any of the time series readers, these methods will try to use some of the default `Table` readers and then require users to specify the names of the important columns.

### Examples

If you are reading in a file called `sampled.csv` where the time column is called `Date` and is an ISO string, you can do:

    >>> from astropy.timeseries import TimeSeries
    >>> from astropy.utils.data import get_pkg_data_filename
    >>> sampled_filename = get_pkg_data_filename('data/sampled.csv',
    ...                                          package='astropy.timeseries.tests')
    >>> ts = TimeSeries.read(sampled_filename, format='ascii.csv',
    ...                      time_column='Date')
    >>> ts[:3]
    <TimeSeries length=3>
              time             A       B       C       D       E       F       G
              Time          float64 float64 float64 float64 float64 float64 float64
    ----------------------- ------- ------- ------- ------- ------- ------- -------
    2008-03-18 00:00:00.000   24.68  164.93  114.73   26.27   19.21   28.87   63.44
    2008-03-19 00:00:00.000   24.18  164.89  114.75   26.22   19.07   27.76   59.98
    2008-03-20 00:00:00.000   23.99  164.63  115.04   25.78   19.01   27.04   59.61

If you are reading in a binned time series from a file called `binned.csv` and with a column `time_start` giving the start time and `bin_size` giving the size of each bin, you can do:

    >>> from astropy import units as u
    >>> from astropy.timeseries import BinnedTimeSeries
    >>> binned_filename = get_pkg_data_filename('data/binned.csv',
    ...                                          package='astropy.timeseries.tests')
    >>> ts = BinnedTimeSeries.read(binned_filename, format='ascii.csv',
    ...                            time_bin_start_column='time_start',
    ...                            time_bin_size_column='bin_size',
    ...                            time_bin_size_unit=u.s)
    >>> ts[:3]
    <BinnedTimeSeries length=3>
         time_bin_start     time_bin_size ...    E       F
                                  s       ...
              Time             float64    ... float64 float64
    ----------------------- ------------- ... ------- -------
    2016-03-22T12:30:31.000           3.0 ...   28.87   63.44
    2016-03-22T12:30:34.000           3.0 ...   27.76   59.98
    2016-03-22T12:30:37.000           3.0 ...   27.04   59.61

See the documentation for `TimeSeries.read` and `BinnedTimeSeries.read` for more details.

Alternatively, you can read in the table using your own code then construct the |TimeSeries| object as described in Creating Time Series, although then you cannot write out another time series in the same format.

If you have written a reader/writer for a commonly used format, please feel free to contribute it to `astropy`!