Reading Offline tracks

The following example shows how to access tracks data in an offline ROOT file.

Note: the offline files used here were intentionaly reduced to 10 events.

import km3io as ki
from km3net_testdata import data_path

We open the file using the

f = ki.OfflineReader(data_path("offline/numucc.root"))

To access offline tracks/mc_tracks data:

f.tracks
f.mc_tracks

<Branch [10] path='mc_trks'>

Note that no data is loaded in memory at this point, so printing tracks will only return how many sub-branches (corresponding to events) were found.

f.tracks

<Branch [10] path='trks'>

same for mc hits

f.mc_tracks

<Branch [10] path='mc_trks'>

Accessing the tracks/mc_tracks keys

to explore the reconstructed tracks fields:

f.tracks.fields

['id', 'pos_x', 'pos_y', 'pos_z', 'dir_x', 'dir_y', 'dir_z', 't', 'E', 'len', 'lik', 'rec_type', 'rec_stages', 'fitinf']

the same for MC tracks

f.mc_tracks.fields

['id', 'pos_x', 'pos_y', 'pos_z', 'dir_x', 'dir_y', 'dir_z', 'E', 't', 'len', 'pdgid', 'hit_ids', 'usr', 'usr_names']

Accessing tracks data

each field will return a nested awkward.Array and load everything into memory, so be careful if you are working with larger files.

f.tracks.E

<Array [[117, 117, 0, 0, 0, ... 0, 0, 0, 0, 0]] type='10 * var * float64'>

The z direction of all reconstructed tracks

f.tracks.dir_z

<Array [[0.213, 0.213, ... -0.158, -0.134]] type='10 * var * float64'>

The likelihoods

f.tracks.lik

<Array [[92.8, 92.8, 92.8, 92.8, ... 0, 0, 0]] type='10 * var * float64'>

To select just a single event or a subset of events, use the indices or slices. The following will access all tracks and their fields of the third event (0 is the first):

f[2].tracks

<Branch [1/10] path='trks'>

The z direction of all tracks in the third event:

f[2].tracks.dir_z

<Array [-0.982, -0.982, ... -0.0365, -0.981] type='38 * float64'>

while here, we select the first 3 events. Notice that all fields will return nested arrays, as we have seem above where all events were selected.

f[:3]

<OfflineReader [3/10] path='E/Evt'>

All tracks for the first three events

f[:3].tracks

<Branch [3/10] path='trks'>

The z directions of all tracks of the first three events

f[:3].tracks.dir_z

<Array [[0.213, 0.213, ... -0.0365, -0.981]] type='3 * var * float64'>

or events from 3 and 5 (again, 0 indexing):

f[2:5]

<OfflineReader [3/10] path='E/Evt'>

the tracks of those events

f[2:5].tracks

<Branch [3/10] path='trks'>

and just the z directions of those

f[2:5].tracks.dir_z

<Array [[-0.982, -0.982, -0.982, ... []] type='3 * var * float64'>

Estimated memory usage: 9 MB