<div dir="ltr">Hi all, <div><br></div><div>I am trying to compute vorticity for a fire snapshot. I've put down a sphere (sp), and can access some other derived fields, but for some reason things like vorticity give me the following error. Does anyone have suggestions as to what I'm doing wrong? </div><div><br></div><div><div style="font-size:12.8px">>>> sp['gas','velocity_magnitude']</div><div style="font-size:12.8px">YTArray([ 53724618.56288539,  48756921.3449135 ,  46197475.78549621, ...,</div><div style="font-size:12.8px">        53664392.60568497,  46881343.68564206,  50050673.058614  ]) cm/s</div><div style="font-size:12.8px">>>> sp['gas','vorticity_x']</div><div style="font-size:12.8px">Traceback (most recent call last):</div><div style="font-size:12.8px">  File "<stdin>", line 1, in <module></div><div style="font-size:12.8px">  File "/home/prachi/anaconda2/lib/<wbr>python2.7/site-packages/yt/<wbr>data_objects/data_containers.<wbr>py", line 281, in __getitem__</div><div style="font-size:12.8px">    self.get_data(f)</div><div style="font-size:12.8px">  File "/home/prachi/anaconda2/lib/<wbr>python2.7/site-packages/yt/<wbr>data_objects/data_containers.<wbr>py", line 1295, in get_data</div><div style="font-size:12.8px">    self._generate_fields(fields_<wbr>to_generate)</div><div style="font-size:12.8px">  File "/home/prachi/anaconda2/lib/<wbr>python2.7/site-packages/yt/<wbr>data_objects/data_containers.<wbr>py", line 1315, in _generate_fields</div><div style="font-size:12.8px">    fd = self._generate_field(field)</div><div style="font-size:12.8px">  File "/home/prachi/anaconda2/lib/<wbr>python2.7/site-packages/yt/<wbr>data_objects/data_containers.<wbr>py", line 318, in _generate_field</div><div style="font-size:12.8px">    tr = self._generate_fluid_field(<wbr>field)</div><div style="font-size:12.8px">  File "/home/prachi/anaconda2/lib/<wbr>python2.7/site-packages/yt/<wbr>data_objects/data_containers.<wbr>py", line 336, in _generate_fluid_field</div><div style="font-size:12.8px">    rv = self._generate_spatial_fluid(<wbr>field, ngt_exception.ghost_zones)</div><div style="font-size:12.8px">  File "/home/prachi/anaconda2/lib/<wbr>python2.7/site-packages/yt/<wbr>data_objects/data_containers.<wbr>py", line 359, in _generate_spatial_fluid</div><div style="font-size:12.8px">    for i, chunk in enumerate(chunks):</div><div style="font-size:12.8px">  File "/home/prachi/anaconda2/lib/<wbr>python2.7/site-packages/yt/<wbr>geometry/particle_geometry_<wbr>handler.py", line 179, in _chunk_spatial</div><div style="font-size:12.8px">    g = og.retrieve_ghost_zones(ngz, [], smoothed=True)</div><div style="font-size:12.8px">AttributeError: 'ParticleOctreeSubset' object has no attribute 'retrieve_ghost_zones'</div></div></div>