Make wavelength bands truly optional

docs/examples/sans2d.ipynb

@@ -60,10 +60,8 @@
     "params[DirectBeamFilename] = 'DIRECT_SANS2D_REAR_34327_4m_8mm_16Feb16.hdf5'\n",
     "params[OutFilename] = 'reduced.nxs'\n",
     "\n",
-    "band = sc.linspace('wavelength', 2.0, 16.0, num=2, unit='angstrom')\n",
-    "params[WavelengthBands] = band\n",
     "params[WavelengthBins] = sc.linspace(\n",
-    "    'wavelength', start=band[0], stop=band[-1], num=141\n",
+    "    'wavelength', start=2.0, stop=16.0, num=141, unit='angstrom'\n",
     ")\n",
     "\n",
     "params[sans.sans2d.LowCountThreshold] = sc.scalar(100, unit='counts')\n",
@@ -229,6 +227,8 @@
    "metadata": {},
    "outputs": [],
    "source": [
+    "from esssans.isis import plot_flat_detector_xy\n",
+    "\n",
     "monitors = (\n",
     "    WavelengthMonitor[SampleRun, Incident],\n",
     "    WavelengthMonitor[SampleRun, Transmission],\n",
@@ -243,14 +243,7 @@
     "\n",
     "display(sc.plot({str(key): results[key] for key in monitors}, norm='log'))\n",
     "\n",
-    "display(\n",
-    "    scn.instrument_view(\n",
-    "        results[MaskedData[SampleRun]].hist(),\n",
-    "        pixel_size=0.0075,\n",
-    "        norm='log',\n",
-    "        camera=pp.graphics.Camera(position=(0, 0, 22)),\n",
-    "    )\n",
-    ")\n",
+    "display(plot_flat_detector_xy(results[MaskedData[SampleRun]].sum('tof'), norm='log'))\n",
     "\n",
     "parts = {str(key): results[key] for key in parts}\n",
     "parts = {key: val if val.bins is None else val.hist() for key, val in parts.items()}\n",
@@ -312,7 +305,7 @@
     "We can also compute $I(Q)$ inside a set of wavelength bands, instead of using the full wavelength range in one go.\n",
     "This is useful for debugging purposes.\n",
     "\n",
-    "To achieve this, we need to turn the `WavelengthBands` parameter into a two-dimensional variable,\n",
+    "To achieve this, we need to supply the `WavelengthBands` parameter (as a two-dimensional variable),\n",
     "representing the wavelength range for each band."
    ]
   },

docs/examples/zoom.ipynb

@@ -100,10 +100,8 @@
     "params[NeXusMonitorName[Incident]] = 'monitor3'\n",
     "params[NeXusMonitorName[Transmission]] = 'monitor5'\n",
     "\n",
-    "band = sc.linspace('wavelength', 1.75, 16.5, num=2, unit='angstrom')\n",
-    "params[WavelengthBands] = band\n",
     "params[WavelengthBins] = sc.geomspace(\n",
-    "    'wavelength', start=band[0], stop=band[-1], num=141\n",
+    "    'wavelength', start=1.75, stop=16.5, num=141, unit='angstrom'\n",
     ")\n",
     "\n",
     "params[QBins] = sc.geomspace(dim='Q', start=0.004, stop=0.8, num=141, unit='1/angstrom')\n",
@@ -271,8 +269,7 @@
    "mimetype": "text/x-python",
    "name": "python",
    "nbconvert_exporter": "python",
-   "pygments_lexer": "ipython3",
-   "version": "3.10.12"
+   "pygments_lexer": "ipython3"
   }
  },
  "nbformat": 4,

src/esssans/beam_center_finder.py

@@ -29,7 +29,6 @@
     QBins,
     SampleRun,
     UncertaintyBroadcastMode,
-    WavelengthBands,
     WavelengthBins,
 )
 
@@ -129,7 +128,7 @@ def _iofq_in_quadrants(
     norm: sc.DataArray,
     graph: dict,
     q_bins: Union[int, sc.Variable],
-    wavelength_range: sc.Variable,
+    wavelength_bins: sc.Variable,
     transform: sc.Variable,
     pixel_shape: sc.DataGroup,
 ) -> Dict[str, sc.DataArray]:
@@ -148,8 +147,8 @@ def _iofq_in_quadrants(
         Coordinate transformation graph.
     q_bins:
         Bin edges for Q.
-    wavelength_range:
-        The wavelength range to use for computing the intensity as a function of Q.
+    wavelength_bins:
+        The binning in wavelength to use for computing the intensity as a function of Q.
 
     Returns
     -------
@@ -177,7 +176,7 @@ def _iofq_in_quadrants(
     ]
     params = {}
     params[UncertaintyBroadcastMode] = UncertaintyBroadcastMode.upper_bound
-    params[WavelengthBands] = wavelength_range
+    params[WavelengthBins] = wavelength_bins
     params[QBins] = q_bins
     params[DetectorPixelShape[SampleRun]] = pixel_shape
     params[LabFrameTransform[SampleRun]] = transform
@@ -405,10 +404,6 @@ def beam_center_from_iofq(
     com_shift = beam_center_from_center_of_mass(data, graph)
     logger.info(f'Initial guess for beam center: {com_shift}')
 
-    wavelength_range = sc.concat(
-        [wavelength_bins.min(), wavelength_bins.max()], dim='wavelength'
-    )
-
     coords = data.transform_coords(
         ['cylindrical_x', 'cylindrical_y'], graph=graph
     ).coords
@@ -421,7 +416,7 @@ def beam_center_from_iofq(
     res = minimize(
         _cost,
         x0=[com_shift.fields.x.value, com_shift.fields.y.value],
-        args=(data, norm, graph, q_bins, wavelength_range, transform, pixel_shape),
+        args=(data, norm, graph, q_bins, wavelength_bins, transform, pixel_shape),
         bounds=bounds,
         method=minimizer,
         tol=tolerance,

src/esssans/i_of_q.py

@@ -131,6 +131,7 @@ def resample_direct_beam(
 
 def _process_wavelength_bands(
     wavelength_bands: Optional[WavelengthBands],
+    wavelength_bins: WavelengthBins,
 ) -> Optional[WavelengthBands]:
     """
     Perform some checks and potential reshaping on the wavelength bands.
@@ -143,7 +144,9 @@ def _process_wavelength_bands(
     and an end wavelength.
     """
     if wavelength_bands is None:
-        return wavelength_bands
+        wavelength_bands = sc.concat(
+            [wavelength_bins.min(), wavelength_bins.max()], dim='wavelength'
+        )
     if wavelength_bands.ndim == 1:
         wavelength_bands = sc.concat(
             [wavelength_bands[:-1], wavelength_bands[1:]], dim='x'
@@ -165,6 +168,7 @@ def _process_wavelength_bands(
 def merge_spectra(
     data: CleanQ[RunType, IofQPart],
     q_bins: QBins,
+    wavelength_bins: WavelengthBins,
     wavelength_bands: Optional[WavelengthBands],
     dims_to_keep: Optional[DimsToKeep],
 ) -> CleanSummedQ[RunType, IofQPart]:
@@ -180,6 +184,8 @@ def merge_spectra(
         A DataArray containing the data that is to be converted to Q.
     q_bins:
         The binning in Q to be used.
+    wavelength_bins:
+        The binning in wavelength to be used.
     wavelength_bands:
         Defines bands in wavelength that can be used to separate different wavelength
         ranges that contribute to different regions in Q space. Note that this needs to
@@ -198,7 +204,9 @@ def merge_spectra(
     if dims_to_keep is not None:
         dims_to_reduce -= set(dims_to_keep)
 
-    wavelength_bands = _process_wavelength_bands(wavelength_bands)
+    wavelength_bands = _process_wavelength_bands(
+        wavelength_bands=wavelength_bands, wavelength_bins=wavelength_bins
+    )
 
     if data.bins is not None:
         out = _events_merge_spectra(
@@ -231,17 +239,14 @@ def _events_merge_spectra(
     data_q: sc.DataArray,
     q_bins: Union[int, sc.Variable],
     dims_to_reduce: List[str],
-    wavelength_bands: Optional[sc.Variable] = None,
+    wavelength_bands: sc.Variable,
 ) -> sc.DataArray:
     """
     Merge spectra of event data
     """
     q_all_pixels = data_q.bins.concat(dims_to_reduce)
     edges = _to_q_bins(q_bins)
     q_binned = q_all_pixels.bin(**edges)
-    if wavelength_bands is None:
-        return q_binned
-
     dim = 'wavelength'
     wav_binned = q_binned.bin({dim: sc.sort(wavelength_bands.flatten(to=dim), dim)})
     # At this point we kind of already have what we need, would be cheapest to just
@@ -263,14 +268,12 @@ def _dense_merge_spectra(
     data_q: sc.DataArray,
     q_bins: Union[int, sc.Variable],
     dims_to_reduce: List[str],
-    wavelength_bands: Optional[sc.Variable] = None,
+    wavelength_bands: sc.Variable,
 ) -> sc.DataArray:
     """
     Merge spectra of dense data
     """
     edges = _to_q_bins(q_bins)
-    if wavelength_bands is None:
-        return data_q.hist(**edges).sum(dims_to_reduce)
     bands = []
     band_dim = (set(wavelength_bands.dims) - {'wavelength'}).pop()
     for wav_range in sc.collapse(wavelength_bands, keep='wavelength').values():

tests/sans2d/reduction_test.py

@@ -34,10 +34,8 @@
 
 def make_params() -> dict:
     params = default_parameters.copy()
-    band = sc.linspace('wavelength', 2.0, 16.0, num=2, unit='angstrom')
-    params[WavelengthBands] = band
     params[WavelengthBins] = sc.linspace(
-        'wavelength', start=band[0], stop=band[-1], num=141
+        'wavelength', start=2.0, stop=16.0, num=141, unit='angstrom'
     )
     params[WavelengthMask] = sc.DataArray(
         data=sc.array(dims=['wavelength'], values=[True]),
@@ -100,6 +98,19 @@ def test_pipeline_can_compute_background_subtracted_IofQ_in_wavelength_slices():
     assert result.sizes['band'] == 10
 
 
+def test_pipeline_wavelength_bands_is_optional():
+    params = make_params()
+    pipeline = sciline.Pipeline(sans2d_providers(), params=params)
+    noband = pipeline.compute(BackgroundSubtractedIofQ)
+    with pytest.raises(sciline.UnsatisfiedRequirement):
+        pipeline.compute(WavelengthBands)
+    band = sc.linspace('wavelength', 2.0, 16.0, num=2, unit='angstrom')
+    pipeline[WavelengthBands] = band
+    assert sc.identical(band, pipeline.compute(WavelengthBands))
+    withband = pipeline.compute(BackgroundSubtractedIofQ)
+    assert sc.identical(noband, withband)
+
+
 def test_workflow_is_deterministic():
     params = make_params()
     params[UncertaintyBroadcastMode] = UncertaintyBroadcastMode.drop