Hi everyone, I'm currently using the PPVcube function to make FITS files of a gizmo simulation. I would like the field used to make the cubes to be mass rather than density. The cube is created however, when I try to write the cube, I get the error copied below. I included the code directly before it. Is it not possible to write FITS cubes with other fields? Cheers, Sam cubeL = PPVCube(ds, L, ("gas","cell_mass"), (-150.,150.,6,"km/s"), dim s=100, method="sum", center=c,width=(0.01, "Mpc"), data_source=sp) cubeL.write_fits("mass.fits",length_unit="kpc", clobber='True')-------------------------------------------------------------------- ------- KeyError Traceback (most recent cal l last) <ipython-input-9-4e7ff69a0d0f> in <module>() ----> 1 cubeL.write_fits("mass.fits",length_unit="kpc", clobber='Tru e') /anaconda2/lib/python2.7/site-packages/yt/utilities/parallel_tools/p arallel_analysis_interface.pyc in root_only(*args, **kwargs) 317 318 --> 319 320 321 def root_only(*args, **kwargs): if not parallel_capable: return func(*args, **kwargs) comm = _get_comm(args) rv = None /anaconda2/lib/python2.7/site-packages/yt/analysis_modules/ppv_cube/ ppv_cube.pyc in write_fits(self, filename, overwrite, length_unit, s ky_scale, sky_center, **kwargs) 313 314 --> 315 317 fib.update_all_headers("btype", self.field) /anaconda2/lib/python2.7/site-packages/yt/visualization/fits_image.p yc in __init__(self, data, fields, units, width, wcs) w.wcs.ctype = ["LINEAR","LINEAR",vtype] fib = FITSImageData(self.data.transpose(), fields=se fib.update_all_headers("bunit", re.sub('()', '', str (self.proj_units))) lf.field, wcs=w)316 158 159 --> 160 161 eld].units)162 KeyError: 'cell_mass'