DataFrameExtractor

Warning: This section is a bit technical and many users won’t need this functionality. Also, it is a bit experimental and the API may change in future versions. Proceed with caution.

The callables `picks_to_df, events_to_df <../datastructures/events_to_pandas.ipynb>`__, and `inventory_to_df <../datastructures/stations_to_pandas.ipynb>`__ are instances of DataFrameExtractor, which provides an extensible and customizable way for creating callables that extract DataFrames from arbitrary objects.

To demonstrate, let’s create a new extractor to put arrival objects in the Crandall catalog into a dataframe. The table can be joined together with the picks table to do some (possibly) interesting things.

import obspy

import obsplus

crandall = obsplus.load_dataset("crandall_test")
cat = crandall.event_client.get_events()

Start by initializing the extractor with a list of expected columns and data types. This is optional, but helps ensure the output dataframe has a consistent shape and data type. The arrival documentation may be useful to understand these. Rather than collecting all the data contained in the Arrival instances, only a few columns of interest will be created.

from collections import OrderedDict

import obspy.core.event as ev

# declare datatypes (order to double as required columns)
dtypes = OrderedDict(
    resource_id=str,
    pick_id=str,
    event_id=str,
    origin_id=str,
    phase=str,
    time_correction=float,
    distance=float,
    time_residual=float,
    time_weight=float,
)

# init the DataFrameExtractor
arrivals_to_df = obsplus.DataFrameExtractor(
    ev.Arrival, required_columns=list(dtypes), dtypes=dtypes
)

The next step it to define some “extractors”. These are callables that will take an Arrival instance and return the desired data. The extractors can return:

1. A dict of values where each key corresponds to a column name and each value is the row value of that column for the current object.

2. Anything else, which is interpreted as the row value, and the column name is obtained from the function name.

# an extractor which returns a dictionary
@arrivals_to_df.extractor
def _get_basic(arrival):
    out = dict(
        resource_id=str(arrival.resource_id),
        pick_id=str(arrival.pick_id),
        time_correction=arrival.time_correction,
        distance=arrival.distance,
        time_residual=arrival.time_residual,
        time_weight=arrival.time_weight,
    )
    return out


# an extractor which returns a single value
@arrivals_to_df.extractor
def _get_phase(arrival):
    return arrival.phase

Notice that there is no way of extracting information from the parent Origin or Event objects. The extractor also doesn’t know how to find the arrivals in a Catalog object. Defining the types of data the extractor can operate on, and injecting the event and origin data into arrival rows will accomplish both of these tasks.

@arrivals_to_df.register(obspy.Catalog)
def _get_arrivals_from_catalogs(cat):
    arrivals = []  # a list of arrivals
    extras = {}  # dict of data to inject to arrival level
    for event in cat:
        for origin in event.origins:
            arrivals.extend(origin.arrivals)
            data = dict(event_id=event.resource_id, origin_id=origin.resource_id)
            # use arrival id to inject extra to each arrival row
            extras.update({id(x): data for x in origin.arrivals})
    return arrivals_to_df(arrivals, extras=extras)

The next step is to initiate the extractor.

df = arrivals_to_df(cat)
df.head()

	resource_id	pick_id	event_id	origin_id	phase	time_correction	distance	time_residual	time_weight
0	smi:local/f537bad8-80a4-4296-8e84-551b78a8c614	smi:local/21695672	smi:local/248925	smi:local/404444	P	NaN	0.360	0.057	-1.0
1	smi:local/754c3d1a-ddf9-4769-8f0f-c5e1b39ed1ad	smi:local/21695673	smi:local/248925	smi:local/404444	P	NaN	0.392	0.322	-1.0
2	smi:local/d6fdbf30-7c1b-45a5-9530-b852ac1e2e80	smi:local/21695674	smi:local/248925	smi:local/404444	P	NaN	0.520	0.086	-1.0
3	smi:local/21b3be94-a309-4343-a3d3-c0e48395ec4c	smi:local/21695675	smi:local/248925	smi:local/404444	P	NaN	0.619	0.203	-1.0
4	smi:local/a4fb84c6-32bb-40f1-9417-9d4b6c91f1f4	smi:local/21695676	smi:local/248925	smi:local/404444	S	NaN	0.360	0.580	-1.0

df.phase.value_counts()

phase
pPn    238
P      224
Pb     129
Sb      87
Pg      79
S       66
Sg      53
Pn      53
Sn      22
pPb      3
Name: count, dtype: int64

If only the P phases were needed, the easiest thing to do is filter the dataframe. For demonstration let’s modify our phase extractor so that any row that is not a P phase is skipped. This is done by raising a SkipRow exception which is an attribute of the DataFrameExtractor.

@arrivals_to_df.extractor
def _get_phase(arrival):
    phase = arrival.phase
    if phase.upper() != "P":
        raise arrivals_to_df.SkipRow
    return phase

/home/runner/work/obsplus/obsplus/src/obsplus/structures/dfextractor.py:122: UserWarning: _get_phase is already a registered extractor, overwriting
  warnings.warn(msg)

df = arrivals_to_df(cat)

Get a picks dataframe and perform a left join on the phases:

# get picks and filter out non-P phases
picks = obsplus.picks_to_df(cat)
picks = picks[picks.phase_hint.str.upper() == "P"]

df_merged = df.merge(picks, how="left", right_on="resource_id", left_on="pick_id")

df_merged.head()

	resource_id_x	pick_id	event_id_x	origin_id	phase	time_correction	distance	time_residual	time_weight	resource_id_y	...	agency_id	event_id_y	network	station	location	channel	uncertainty	lower_uncertainty	upper_uncertainty	confidence_level
0	smi:local/f537bad8-80a4-4296-8e84-551b78a8c614	smi:local/21695672	smi:local/248925	smi:local/404444	P	NaN	0.360	0.057	-1.0	smi:local/21695672	...		smi:local/248925	TA	P17A		BHZ	NaN	NaN	NaN	NaN
1	smi:local/754c3d1a-ddf9-4769-8f0f-c5e1b39ed1ad	smi:local/21695673	smi:local/248925	smi:local/404444	P	NaN	0.392	0.322	-1.0	smi:local/21695673	...		smi:local/248925	TA	P16A		BHZ	NaN	NaN	NaN	NaN
2	smi:local/d6fdbf30-7c1b-45a5-9530-b852ac1e2e80	smi:local/21695674	smi:local/248925	smi:local/404444	P	NaN	0.520	0.086	-1.0	smi:local/21695674	...		smi:local/248925	TA	Q16A		BHZ	NaN	NaN	NaN	NaN
3	smi:local/21b3be94-a309-4343-a3d3-c0e48395ec4c	smi:local/21695675	smi:local/248925	smi:local/404444	P	NaN	0.619	0.203	-1.0	smi:local/21695675	...		smi:local/248925	UU	SRU		BHZ	NaN	NaN	NaN	NaN
4	smi:local/344ff568-12b4-4e3d-af56-724c81d07568	smi:local/21695679	smi:local/248925	smi:local/404444	P	NaN	0.763	0.031	-1.0	smi:local/21695679	...		smi:local/248925	TA	P18A		BHZ	NaN	NaN	NaN	NaN

5 rows × 34 columns

df_merged.columns

Index(['resource_id_x', 'pick_id', 'event_id_x', 'origin_id', 'phase',
       'time_correction', 'distance', 'time_residual', 'time_weight',
       'resource_id_y', 'time', 'seed_id', 'filter_id', 'method_id',
       'horizontal_slowness', 'backazimuth', 'onset', 'phase_hint', 'polarity',
       'evaluation_mode', 'event_time', 'evaluation_status', 'creation_time',
       'author', 'agency_id', 'event_id_y', 'network', 'station', 'location',
       'channel', 'uncertainty', 'lower_uncertainty', 'upper_uncertainty',
       'confidence_level'],
      dtype='object')

Calculate how often the phase attribute in the arrival is different from the phase_hint in the pick, which could indicate a quality issue.

# calculate fraction of phase_hints that match phase
(df_merged["phase"] == df_merged["phase_hint"]).sum() / len(df_merged)

np.float64(1.0)