Hi yt-users! I have a list of positions that I call xwclump, ywclump, and zwclump. I have been selecting regions in a loop using ds.sphere and the center: data_source = ds.sphere([xwclump[j]/(300.*3.086e21),ywclump[j]/(300.*3.086e21),zwclump[j]/(300.*3.086e21)],(1000,'pc')) (the divisor is to put the center into code units). This works fine. But, when I try to use cut_region: data_source = ad.cut_region(["(obj['temperature'] > 1.0e6) & (obj['z'] < (zwclump[j]/(300.*3.086e21)))"]) I get an error: NameError: name 'zwclump' is not defined Is this something anyone else has dealt with? If it doesn't ring any bells I will try and break IsolatedGalaxy and send the code snippet... Thanks, Stephanie -- Dr. Stephanie Tonnesen Associate Research Scientist CCA, Flatiron Institute New York, NY stonnes@gmail.com