MEC sys stage

pisa/stages/xsec/mec_sys.py

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+"""
+Systematic uncertainty model for Meson Exchange Current (MEC) events.
+"""
+
+from pisa import ureg
+from pisa.core.param import Param, ParamSet
+from pisa.core.stage import Stage
+from pisa.utils.profiler import profile
+
+__all__ = ["mec_sys", "init_test"]
+
+
+class mec_sys(Stage):  # pylint: disable=invalid-name
+    """
+    Stage to apply MEC event systematic uncertainties
+
+    This is currently just a normalization parameter.
+
+    Parameters
+    ----------
+
+    params : ParamSet
+        Must have parameters::
+            mec_scale : quantity (dimensionless)
+                A normalization to be applied to all MEC events
+
+    Notes
+    -----
+
+    Expected container keys are::
+
+        "mec" - a boolean flag indicating if the event is an MEC interaction
+        "weights" - the event weight that will be modified by this stage
+    """
+
+    def __init__(
+        self,
+        **std_kwargs,
+    ):
+        expected_params = ("mec_scale",)
+
+        expected_container_keys = (
+            "weights",
+            "mec",
+        )
+
+        # init base class
+        super().__init__(
+            expected_params=expected_params,
+            expected_container_keys=expected_container_keys,
+            **std_kwargs,
+        )
+
+    @profile
+    def apply_function(self):
+
+        # Get the normalization parameter, and use it to scale the weights of all events that
+        # are marked by the "mec" flag.
+
+        mec_scale = self.params.mec_scale.m_as("dimensionless")
+
+        for container in self.data:
+            mec = container["mec"].astype(bool)
+            if mec.sum() > 0:
+                container["weights"][mec] *= mec_scale
+                container.mark_changed("weights")
+
+
+def init_test(**param_kwargs):
+    """Instantiation example"""
+    param_set = ParamSet([Param(name="mec_scale", value=1.0, **param_kwargs)])
+
+    return mec_sys(params=param_set)