Add method to read the shower distributions to table loader

ctapipe/io/tableloader.py

@@ -29,6 +29,7 @@
 TRUE_PARAMETERS_GROUP = "/simulation/event/telescope/parameters"
 TRUE_IMPACT_GROUP = "/simulation/event/telescope/impact"
 SIMULATION_CONFIG_TABLE = "/configuration/simulation/run"
+SHOWER_DISTRIBUTION_TABLE = "/simulation/service/shower_distribution"
 
 DL2_SUBARRAY_GROUP = "/dl2/event/subarray"
 DL2_TELESCOPE_GROUP = "/dl2/event/telescope"
@@ -306,6 +307,12 @@ def read_simulation_configuration(self):
         """
         return read_table(self.h5file, SIMULATION_CONFIG_TABLE)
 
+    def read_shower_distribution(self):
+        """
+        Read the simulated shower distribution histograms
+        """
+        return read_table(self.h5file, SHOWER_DISTRIBUTION_TABLE)
+
     def read_subarray_events(self, start=None, stop=None, keep_order=True):
         """Read subarray-based event information.
 

ctapipe/io/tests/test_table_loader.py

@@ -352,3 +352,14 @@ def test_read_simulation_config(dl2_merged_file):
         assert len(runs) == 2
         assert np.all(runs["obs_id"] == [4, 1])
         assert u.allclose(runs["energy_range_min"].quantity, [0.004, 0.003] * u.TeV)
+
+
+def test_read_shower_distributions(dl2_merged_file):
+    from ctapipe.io import TableLoader
+
+    with TableLoader(dl2_merged_file) as table_loader:
+        histograms = table_loader.read_shower_distribution()
+        assert len(histograms) == 2
+        assert np.all(histograms["obs_id"] == [4, 1])
+        assert np.all(histograms["num_entries"] == [2000, 1000])
+        assert np.all(histograms["histogram"].sum(axis=(1, 2)) == [2000, 1000])