.. DO NOT EDIT. .. THIS FILE WAS AUTOMATICALLY GENERATED BY SPHINX-GALLERY. .. TO MAKE CHANGES, EDIT THE SOURCE PYTHON FILE: .. "tutorials/api/observation_clustering.py" .. LINE NUMBERS ARE GIVEN BELOW. .. only:: html .. note:: :class: sphx-glr-download-link-note :ref:`Go to the end ` to download the full example code. or to run this example in your browser via Binder .. rst-class:: sphx-glr-example-title .. _sphx_glr_tutorials_api_observation_clustering.py: Observational clustering ======================== Clustering observations into specific groups. Context ------- Typically, observations from gamma-ray telescopes can span a number of different observation periods, therefore it is likely that the observation conditions and quality are not always the same. This tutorial aims to provide a way in which observations can be grouped such that similar observations are grouped together, and then the data reduction is performed. Objective --------- To cluster similar observations based on various quantities. Proposed approach ----------------- For completeness two different methods for grouping of observations are shown here. - A simple grouping based on zenith angle from an existing observations table. - Grouping the observations depending on the IRF quality, by means of hierarchical clustering. .. GENERATED FROM PYTHON SOURCE LINES 33-42 .. code-block:: Python import numpy as np import astropy.units as u from astropy.coordinates import SkyCoord import matplotlib.pyplot as plt from gammapy.data import DataStore from gammapy.data.utils import get_irfs_features from gammapy.utils.cluster import hierarchical_clustering, standard_scaler .. GENERATED FROM PYTHON SOURCE LINES 43-52 Obtain the observations ----------------------- First need to define the `~gammapy.data.DataStore` object for the H.E.S.S. DL3 DR1 data. Next, utilise a cone search to select only the observations of interest. In this case, we choose PKS 2155-304 as the object of interest. The `~gammapy.data.ObservationTable` is then filtered using the `select_observations` tool. .. GENERATED FROM PYTHON SOURCE LINES 52-66 .. code-block:: Python data_store = DataStore.from_dir("$GAMMAPY_DATA/hess-dl3-dr1") selection = dict( type="sky_circle", frame="icrs", lon="329.71693826 deg", lat="-30.2255 deg", radius="2 deg", ) obs_table = data_store.obs_table selected_obs_table = obs_table.select_observations(selection) .. GENERATED FROM PYTHON SOURCE LINES 67-71 More complex selection can be done by utilising the obs_table entries directly. We can now retrieve the relevant observations by passing their obs_id to the `~gammapy.data.DataStore.get_observations` method. .. GENERATED FROM PYTHON SOURCE LINES 71-76 .. code-block:: Python obs_ids = selected_obs_table["OBS_ID"] observations = data_store.get_observations(obs_ids) .. GENERATED FROM PYTHON SOURCE LINES 77-83 Show various observation quantities ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Print here the range of zenith angles and muon efficiencies, to see if there is a sensible way to group the observations. .. GENERATED FROM PYTHON SOURCE LINES 83-91 .. code-block:: Python obs_zenith = selected_obs_table["ZEN_PNT"].to(u.deg) obs_muoneff = selected_obs_table["MUONEFF"] print(f"{np.min(obs_zenith):.2f} < zenith angle < {np.max(obs_zenith):.2f}") print(f"{np.min(obs_muoneff):.2f} < muon efficiency < {np.max(obs_muoneff):.2f}") .. rst-class:: sphx-glr-script-out .. code-block:: none 7.23 deg < zenith angle < 50.42 deg 0.97 < muon efficiency < 1.03 .. GENERATED FROM PYTHON SOURCE LINES 92-104 Manual grouping of observations ------------------------------- Here we can plot the zenith angle vs muon efficiency of the observations. We decide to group the observations according to their zenith angle. This is done manually as per a user defined cut, in this case we take the median value of the zenith angles to define each observation group. This type of grouping can be utilised according to different parameters i.e. zenith angle, muon efficiency, offset angle. The quantity chosen can therefore be adjusted according to each specific science case. .. GENERATED FROM PYTHON SOURCE LINES 104-115 .. code-block:: Python median_zenith = np.median(obs_zenith) labels = [] for obs in observations: zenith = obs.get_pointing_altaz(time=obs.tmid).zen labels.append("low_zenith" if zenith < median_zenith else "high_zenith") grouped_observations = observations.group_by_label(labels) print(grouped_observations) .. rst-class:: sphx-glr-script-out .. code-block:: none {'group_high_zenith': , 'group_low_zenith': } .. GENERATED FROM PYTHON SOURCE LINES 116-118 The results for each group of observations is shown visually below. .. GENERATED FROM PYTHON SOURCE LINES 119-141 .. code-block:: Python fix, ax = plt.subplots(1, 1, figsize=(7, 5)) for obs in grouped_observations["group_low_zenith"]: ax.plot( obs.get_pointing_altaz(time=obs.tmid).zen, obs.meta.optional["MUONEFF"], "d", color="red", ) for obs in grouped_observations["group_high_zenith"]: ax.plot( obs.get_pointing_altaz(time=obs.tmid).zen, obs.meta.optional["MUONEFF"], "o", color="blue", ) ax.set_ylabel("Muon efficiency") ax.set_xlabel("Zenith angle (deg)") ax.axvline(median_zenith.value, ls="--", color="black") plt.show() .. image-sg:: /tutorials/api/images/sphx_glr_observation_clustering_001.png :alt: observation clustering :srcset: /tutorials/api/images/sphx_glr_observation_clustering_001.png :class: sphx-glr-single-img .. GENERATED FROM PYTHON SOURCE LINES 142-150 This shows the observations grouped by zenith angle. The diamonds are observations which have a zenith angle less than the median value, whilst the circles are observations above the median. The `grouped_observations` provide a list of `~gammapy.data.Observations` which can be utilised in the usual way to show the various properties of the observations i.e. see the :doc:`/tutorials/data/cta` tutorial. .. GENERATED FROM PYTHON SOURCE LINES 153-167 Hierarchical clustering of observations --------------------------------------- This method shows how to cluster observations based on their IRF quantities, in this case those that have a similar edisp and psf. The `~gammapy.data.utils.get_irfs_features` is utilised to achieve this. The observations are then clustered based on these criteria using `~gammapy.utils.cluster.hierarchical_clustering`. The idea here is to minimise the variance of both edisp and psf within a specific group to limit the error on the quantity when they are stacked at the dataset level. In this example, the irf features are computed for the `edisp-res` and `psf-radius` at 1 TeV. This is stored as a `~astropy.table.table.Table`, as shown below. .. GENERATED FROM PYTHON SOURCE LINES 167-175 .. code-block:: Python source_position = SkyCoord(329.71693826 * u.deg, -30.2255890 * u.deg, frame="icrs") names = ["edisp-res", "psf-radius"] features_irfs = get_irfs_features( observations, energy_true="1 TeV", position=source_position, names=names ) print(features_irfs) .. rst-class:: sphx-glr-script-out .. code-block:: none edisp-res obs_id psf-radius deg ------------------- ------ ------------------- 0.36834038301420274 33787 0.14149953611195087 0.339835555384604 33788 0.11553325504064559 0.3237948931463171 33789 0.10262943822890519 0.30535345877453707 33790 0.09426693227142095 0.28755283551095173 33791 0.08894569035619496 0.27409496735322464 33792 0.08447355125099419 0.26665050077722524 33793 0.0811551760882139 0.26272868097919794 33794 0.07943648658692837 0.2639554729438709 33795 0.0799109224230051 0.26887783978974283 33796 0.08191603310406206 0.2777074437073429 33797 0.0855013383552432 0.29355238360800506 33798 0.0897868126630783 0.31186857659616535 33799 0.09623312838375568 0.33164865722698683 33800 0.10470702368766069 0.3503706026275275 33801 0.12276676166802643 0.3011061699260256 47802 0.09740295372903346 0.2861432787940619 47803 0.08880368117243051 0.27057337686547633 47804 0.08388624433428049 0.29882214027996945 47827 0.09610314778983592 0.28385358839966657 47828 0.08795162606984375 0.268663733018811 47829 0.08328557573258877 .. GENERATED FROM PYTHON SOURCE LINES 176-179 Compute standardized features by removing the mean and scaling to unit variance: .. GENERATED FROM PYTHON SOURCE LINES 179-184 .. code-block:: Python scaled_features_irfs = standard_scaler(features_irfs) print(scaled_features_irfs) .. rst-class:: sphx-glr-script-out .. code-block:: none edisp-res obs_id psf-radius -------------------- ------ --------------------- 2.3885947175689592 33787 3.053212009682775 1.4351637481047363 33788 1.363472509034498 0.8986348363207728 33789 0.5237647004325865 0.2818047723094509 33790 -0.020420144596410953 -0.3135914081482271 33791 -0.36669663417038234 -0.7637308880733709 33792 -0.6577182894355391 -1.012733796525585 33793 -0.873659477745188 -1.1439110308062257 33794 -0.985502122122975 -1.102877228833871 33795 -0.9546285068162436 -0.9382336444241555 33796 -0.8241471833009617 -0.6429005895278312 33797 -0.590835686434463 -0.11291820875721864 33798 -0.3119611261122878 0.49972277488662115 33799 0.10752883769757363 1.1613279491744304 33800 0.6589622747787678 1.7875405607868806 33801 1.8341884287660133 0.1397412321592923 47802 0.1836544903987521 -0.36073833513766157 47803 -0.3759377929871826 -0.8815212313941426 47804 -0.6959369197218669 0.06334488877417636 47827 0.09907043184188653 -0.4373240195300975 47828 -0.4313847458879893 -0.9453950989269149 47829 -0.7350250533013533 .. GENERATED FROM PYTHON SOURCE LINES 185-194 The `~gammapy.utils.cluster.hierarchical_clustering` then clusters this table into ``t=2`` groups with a corresponding label for each group. In this case, we choose to cluster the observations into two groups. We can print this table to show the corresponding label which has been added to the previous ``feature_irfs`` table. The arguments for `~scipy.cluster.hierarchy.fcluster` are passed as a dictionary here. .. GENERATED FROM PYTHON SOURCE LINES 194-198 .. code-block:: Python features = hierarchical_clustering(scaled_features_irfs, fcluster_kwargs={"t": 2}) print(features) .. rst-class:: sphx-glr-script-out .. code-block:: none edisp-res obs_id psf-radius labels -------------------- ------ --------------------- ------ 2.3885947175689592 33787 3.053212009682775 1 1.4351637481047363 33788 1.363472509034498 1 0.8986348363207728 33789 0.5237647004325865 1 0.2818047723094509 33790 -0.020420144596410953 2 -0.3135914081482271 33791 -0.36669663417038234 2 -0.7637308880733709 33792 -0.6577182894355391 2 -1.012733796525585 33793 -0.873659477745188 2 -1.1439110308062257 33794 -0.985502122122975 2 -1.102877228833871 33795 -0.9546285068162436 2 -0.9382336444241555 33796 -0.8241471833009617 2 -0.6429005895278312 33797 -0.590835686434463 2 -0.11291820875721864 33798 -0.3119611261122878 2 0.49972277488662115 33799 0.10752883769757363 2 1.1613279491744304 33800 0.6589622747787678 1 1.7875405607868806 33801 1.8341884287660133 1 0.1397412321592923 47802 0.1836544903987521 2 -0.36073833513766157 47803 -0.3759377929871826 2 -0.8815212313941426 47804 -0.6959369197218669 2 0.06334488877417636 47827 0.09907043184188653 2 -0.4373240195300975 47828 -0.4313847458879893 2 -0.9453950989269149 47829 -0.7350250533013533 2 .. GENERATED FROM PYTHON SOURCE LINES 199-202 Finally, ``observations.group_by_label`` creates a dictionary containing ``t`` `~gammapy.data.Observations` objects by grouping the similar labels. .. GENERATED FROM PYTHON SOURCE LINES 202-230 .. code-block:: Python obs_clusters = observations.group_by_label(features["labels"]) print(obs_clusters) mask_1 = features["labels"] == 1 mask_2 = features["labels"] == 2 fix, ax = plt.subplots(1, 1, figsize=(7, 5)) ax.set_ylabel("edisp-res") ax.set_xlabel("psf-radius") ax.plot( features_irfs[mask_1]["edisp-res"], features_irfs[mask_1]["psf-radius"], "d", color="green", label="Group 1", ) ax.plot( features_irfs[mask_2]["edisp-res"], features_irfs[mask_2]["psf-radius"], "o", color="magenta", label="Group 2", ) ax.legend() plt.show() .. image-sg:: /tutorials/api/images/sphx_glr_observation_clustering_002.png :alt: observation clustering :srcset: /tutorials/api/images/sphx_glr_observation_clustering_002.png :class: sphx-glr-single-img .. rst-class:: sphx-glr-script-out .. code-block:: none {'group_1': , 'group_2': } .. GENERATED FROM PYTHON SOURCE LINES 231-241 The groups here are divided by the quality of the IRFs values ``edisp-res`` and ``psf-radius``. The diamond and circular points indicate how the observations are grouped. In both examples we have a set of `~gammapy.data.Observation` objects which can be reduced using the `~gammapy.makers.DatasetsMaker` to create two (in this specific case) separate datasets. These can then be jointly fitted using the :doc:`/tutorials/analysis-3d/analysis_mwl` tutorial. .. _sphx_glr_download_tutorials_api_observation_clustering.py: .. only:: html .. container:: sphx-glr-footer sphx-glr-footer-example .. container:: binder-badge .. image:: images/binder_badge_logo.svg :target: https://mybinder.org/v2/gh/gammapy/gammapy-webpage/v1.3?urlpath=lab/tree/notebooks/1.3/tutorials/api/observation_clustering.ipynb :alt: Launch binder :width: 150 px .. container:: sphx-glr-download sphx-glr-download-jupyter :download:`Download Jupyter notebook: observation_clustering.ipynb ` .. container:: sphx-glr-download sphx-glr-download-python :download:`Download Python source code: observation_clustering.py ` .. container:: sphx-glr-download sphx-glr-download-zip :download:`Download zipped: observation_clustering.zip ` .. only:: html .. rst-class:: sphx-glr-signature `Gallery generated by Sphinx-Gallery `_