Fix moment map when spectral units are in frequency (#2803)

* Fix moment map when spectral units are in frequency

* Update changelog

CHANGES.rst

@@ -7,7 +7,7 @@ New Features
 Cubeviz
 ^^^^^^^
 
-- Enable spectral unit conversion in cubeviz. [#2758]
+- Enable spectral unit conversion in cubeviz. [#2758, #2803]
 
 Imviz
 ^^^^^

jdaviz/configs/cubeviz/plugins/moment_maps/moment_maps.py

@@ -126,6 +126,10 @@ def user_api(self):
                                            'output_unit', 'reference_wavelength',
                                            'add_results', 'calculate_moment'))
 
+    @property
+    def slice_display_unit_name(self):
+        return 'spectral'
+
     @observe('is_active')
     def _is_active_changed(self, msg):
         for pos, mark in self.continuum_marks.items():
@@ -239,6 +243,12 @@ def calculate_moment(self, add_data=True):
         # slice out desired region
         # TODO: should we add a warning for a composite spectral subset?
         spec_min, spec_max = self.spectral_subset.selected_min_max(cube)
+        display_spectral_axis_unit = self.app._get_display_unit(self.slice_display_unit_name)
+
+        # Convert units of min and max if necessary
+        if display_spectral_axis_unit and display_spectral_axis_unit != str(spec_min.unit):
+            spec_min = spec_min.to(display_spectral_axis_unit, equivalencies=u.spectral())
+            spec_max = spec_max.to(display_spectral_axis_unit, equivalencies=u.spectral())
         slab = manipulation.spectral_slab(cube, spec_min, spec_max)
 
         # Calculate the moment and convert to CCDData to add to the viewers

jdaviz/configs/cubeviz/plugins/moment_maps/tests/test_moment_maps.py

@@ -7,7 +7,9 @@
 from astropy.nddata import CCDData
 from astropy.wcs import WCS
 from astroquery.mast import Observations
+import numpy as np
 from numpy.testing import assert_allclose
+from glue.core.roi import XRangeROI
 
 
 def test_user_api(cubeviz_helper, spectrum1d_cube):
@@ -188,6 +190,27 @@ def test_moment_velocity_calculation(cubeviz_helper, spectrum1d_cube):
                                          "204.9997755344 27.0001999998 (deg)")
 
 
+def test_moment_frequency_unit_conversion(cubeviz_helper, spectrum1d_cube_larger):
+    with warnings.catch_warnings():
+        warnings.filterwarnings("ignore", message="No observer defined on WCS.*")
+        cubeviz_helper.load_data(spectrum1d_cube_larger, data_label='test')
+
+    uc = cubeviz_helper.plugins['Unit Conversion']
+    mm = cubeviz_helper.plugins['Moment Maps']
+    viewer = cubeviz_helper.app.get_viewer('spectrum-viewer')
+    viewer.apply_roi(XRangeROI(4.624e-07, 4.627e-07))
+
+    uc.spectral_unit = 'Hz'
+    mm.spectral_subset = 'Subset 1'
+    mm.continuum = 'Surrounding'
+    mm.n_moment = 1
+    mm.output_unit = 'Spectral Unit'
+    moment_1_data = mm.calculate_moment()
+
+    # Check to make sure there are no nans
+    assert len(np.where(moment_1_data.data > 0)[0]) == 8
+
+
 def test_write_momentmap(cubeviz_helper, spectrum1d_cube, tmp_path):
     ''' Test writing a moment map out to a FITS file on disk '''