add idx boolean selection for member and leadtime (#1183)

* add idx boolean selection for member and leadtime
* Add test for weird data types

---------

Co-authored-by: Lukas Riedel <34276446+peanutfun@users.noreply.github.com>

Author: elianekobler

climada/util/forecast.py

@@ -56,3 +56,35 @@ def __init__(
         )
         self.member = np.asarray(member) if member is not None else np.array([])
         super().__init__(**kwargs)
+
+    def idx_member(self, member: np.ndarray) -> np.ndarray:
+        """Return boolean array where self.member == member using numpy.isin()
+
+        Parameters
+        ----------
+        member : np.ndarray
+            Array of ensemble members (ints) for which to return an indexer
+
+        Returns
+        -------
+        np.ndarray
+            Boolean array where self.member is in member.
+        """
+
+        return np.isin(self.member, member)
+
+    def idx_lead_time(self, lead_time: np.ndarray) -> np.ndarray:
+        """Return boolean array where self.lead_time == lead_time using numpy.isin()
+
+        Parameters
+        ----------
+        lead_time : np.ndarray
+            Array of lead times (numpy.timedelta64) for which to return an indexer
+
+        Returns
+        -------
+        np.ndarray
+            Boolean array where self.lead_time is in lead_time.
+        """
+
+        return np.isin(self.lead_time, lead_time)

climada/util/test/test_forecast.py

@@ -50,3 +50,46 @@ def test_forecast_init():
     forecast = Forecast(lead_time=lead_times_seconds, member=[1, 2, 3])
     npt.assert_array_equal(forecast.lead_time, lead_times_seconds, strict=True)
     assert forecast.lead_time.dtype == np.dtype("timedelta64[ns]")
+
+
+def test_idx_member():
+    """Test idx_member method of Forecast class."""
+    forecast = Forecast(member=np.array([1, 2, 3, 4]))
+
+    idx = forecast.idx_member(1)
+    npt.assert_array_equal(idx, np.array([True, False, False, False]), strict=True)
+
+    idx = forecast.idx_member(np.array([2, 4]))
+    npt.assert_array_equal(idx, np.array([False, True, False, True]), strict=True)
+
+    idx = forecast.idx_member([2, 4])
+    npt.assert_array_equal(idx, np.array([False, True, False, True]), strict=True)
+
+    idx = forecast.idx_member(None)
+    npt.assert_array_equal(idx, np.array([False, False, False, False]), strict=True)
+
+    # Try once with inconsitent types
+    forecast = Forecast(member=np.array(["1", -2, np.nan]))
+    npt.assert_array_equal(
+        forecast.idx_member([np.nan, "1"]), np.array([True, False, True]), strict=True
+    )
+
+
+def test_idx_lead_time():
+    """Test idx_lead_time method of Forecast class."""
+    forecast = Forecast(
+        lead_time=pd.timedelta_range(start="1 day", periods=4).to_numpy()
+    )
+
+    idx = forecast.idx_lead_time(
+        pd.timedelta_range(start="1 day", periods=4).to_numpy()[::2]
+    )
+    npt.assert_array_equal(idx, np.array([True, False, True, False]), strict=True)
+
+    idx = forecast.idx_lead_time(
+        pd.timedelta_range(start="1 day", periods=4).to_numpy()[0]
+    )
+    npt.assert_array_equal(idx, np.array([True, False, False, False]), strict=True)
+
+    idx = forecast.idx_lead_time(None)
+    npt.assert_array_equal(idx, np.array([False, False, False, False]), strict=True)