Added axis_channel and num_channel properties to AbstractInstrument. (#8)

Author: roytsmart

ctis/instruments/_instruments.py

@@ -106,6 +106,14 @@ def coordinates_sensor(self) -> na.AbstractSpectralPositionalVectorArray:
         A grid of wavelength and position coordinates on the detector plane.
         """
 
+    @property
+    @abc.abstractmethod
+    def axis_channel(self) -> str | tuple[str, ...]:
+        """
+        The logical axis or axes of this instrument corresponding to
+        the different dispersion magnitudes and angles.
+        """
+
     @property
     @abc.abstractmethod
     def axis_wavelength(self) -> str:
@@ -130,6 +138,14 @@ def axis_sensor_xy(self) -> tuple[str, str]:
         changing position coordinate.
         """
 
+    @property
+    @abc.abstractmethod
+    def num_channel(self) -> int:
+        """
+        The total number of dispersion magnitudes/angles observed by this
+        instrument.
+        """
+
 
 @dataclasses.dataclass
 class AbstractLinearInstrument(
@@ -160,6 +176,21 @@ def weights_transpose(
         skyplane.
         """
 
+    @property
+    def num_channel(self) -> int:
+
+        shape = self.weights[0].shape
+
+        axis_channel = self.axis_channel
+        if isinstance(axis_channel, str):
+            axis_channel = (axis_channel,)
+
+        num_channels = 1
+        for ax in axis_channel:
+            num_channels = num_channels * shape[ax]
+
+        return num_channels
+
     @property
     def _volume_scene(self) -> na.AbstractScalar:
         """
@@ -338,6 +369,12 @@ class IdealInstrument(
     A grid of wavelength and position coordinates on the sensor plane.
     """
 
+    axis_channel: str | tuple[str, ...] = dataclasses.MISSING
+    """
+    The logical axis or axes of this instrument corresponding to
+    the different dispersion magnitudes and angles.
+    """
+
     axis_wavelength: str = dataclasses.MISSING
     """
     The logical axis of :attr:`coordinates_scene` and :attr:`coordinates_sensor`

ctis/instruments/_instruments_test.py

@@ -45,11 +45,12 @@
     timedelta_exposure=10 * u.s,
     plate_scale=2 * u.arcsec / u.pix,
     dispersion=dispersion,
-    angle=0 * u.deg,
+    angle=na.linspace(0, 360, axis="channel", num=3, endpoint=False),
     wavelength_ref=wavelength_rest,
     position_ref=32 * u.pix,
     coordinates_scene=coordinates_scene,
     coordinates_sensor=coordinates_sensor,
+    axis_channel="channel",
     axis_wavelength="wavelength",
     axis_scene_xy=("scene_x", "scene_y"),
     axis_sensor_xy=("sensor_x", "sensor_y"),
@@ -95,6 +96,14 @@ def test_backproject(
 
         assert np.allclose(image.sum(), image_check.sum())
 
+    def test_num_channel(
+        self,
+        a: ctis.instruments.AbstractInstrument,
+    ):
+        result = a.num_channel
+
+        assert isinstance(result, int)
+
 
 class AbstractTestAbstractLinearInstrument(
     AbstractTestAbstractInstrument,

docs/tutorials/ideal-instrument.ipynb

@@ -306,6 +306,7 @@
     "    position_ref=32 * u.pix,\n",
     "    coordinates_scene=coordinates_scene,\n",
     "    coordinates_sensor=coordinates_sensor,\n",
+    "    axis_channel=\"channel\",\n",
     "    axis_wavelength=\"wavelength\",\n",
     "    axis_scene_xy=(\"scene_x\", \"scene_y\"),\n",
     "    axis_sensor_xy=(\"sensor_x\", \"sensor_y\"),\n",