Hi, I’ve encountered a new error when specifying a box using units other than code units. This is a Flash 4 plot file in cgs units. Example: import yt yt.__version__ ‘3.3.3’ d = yt.load('sn34_smd75_sub1_hdf5_plt_cnt_0030') b = d.box([-500,-500,-20]*yt.units.pc.in_cgs(),[500,500,20]*yt.units.pc.in_cgs()) fp = yt.PhasePlot(b,'n','pk',['cell_volume'],weight_field=None, fractional=True) I get the following error: UnitParseError: Code units have not been defined. Try creating the array or quantity using ds.arr or ds.quan instead. If I instead do b = d.box([-1.54e+21, -1.54e+21, -6.17e+19], [1.54e+21, 1.54e+21, 6.17e+19]) or left = d.domain_left_edge right = d.domain_right_edge left[2] = -6.17e19 right[2] = 6.17e19 b = d.box(left, right) I do not get any error. If I specify yt.units.cm, I do get the error. This was not an issue on the same data file a few months ago. I think I have updated yt in the meantime, but I’m not sure what the version was. Is this a bug, or am I doing something wrong? Here is the unit registry for my data set: reg = d.unit_registry for un in reg.keys(): if un.startswith('code_'): fmt_tup = (un, reg.lut[un][0], str(reg.lut[un][1])) print ("Unit name: {:<15}\nCGS conversion: {:<15}\nDimensions: {:<15}\n".format(*fmt_tup)) Unit name: code_magnetic CGS conversion: 1.0 Dimensions: sqrt((mass))/(sqrt((length))*(time)) Unit name: code_time CGS conversion: 1.0 Dimensions: (time) Unit name: code_temperature CGS conversion: 1.0 Dimensions: (temperature) Unit name: code_pressure CGS conversion: 1.0 Dimensions: (mass)/((length)*(time)**2) Unit name: code_mass CGS conversion: 1.0 Dimensions: (mass) Unit name: code_velocity CGS conversion: 1.0 Dimensions: (length)/(time) Unit name: code_length CGS conversion: 1.0 Dimensions: (length) Unit name: code_density CGS conversion: 1.0 Dimensions: (mass)/(length)**3 Unit name: code_metallicity CGS conversion: 1.0 Dimensions: 1 Cheers, Alex