Backport PR yt-project#2504: Add masking for phase plots.

Author: neutrinoceros

answer-store

@@ -94,7 +94,7 @@ answer_tests:
     - yt/frontends/owls/tests/test_outputs.py:test_snapshot_033
     - yt/frontends/owls/tests/test_outputs.py:test_OWLS_particlefilter
 
-  local_pw_041:  # PR 3670
+  local_pw_042:  # PR 2504
     - yt/visualization/tests/test_plotwindow.py:test_attributes
     - yt/visualization/tests/test_particle_plot.py:test_particle_projection_answers
     - yt/visualization/tests/test_particle_plot.py:test_particle_projection_filter

tests/tests.yaml

@@ -1130,10 +1130,12 @@ def _setup_plots(self):
             else:
                 cmap = self._colormap_config[f]
 
+            masked_data = data.copy()
+            masked_data[~self.profile.used] = np.nan
             self.plots[f] = PhasePlotMPL(
                 self.profile.x,
                 self.profile.y,
-                data,
+                masked_data,
                 x_scale,
                 y_scale,
                 z_scale,