Hi guys, one more thing. I want to calculate the radiation pressure force, and when there is some then plot it with a log scale. However if I set: def _ConvertAccel(data): return data.convert("Length") / (data.convert("Time"))**2.0 def _RadiationAccelerationMagnitude(field, data): return ( (data["RadAccel1"])**2.0 + \ (data["RadAccel2"])**2.0 + \ (data["RadAccel3"])**2.0 )**(1.0/2.0) add_field("RadiationAccelerationMagnitude", function=_RadiationAccelerationMagnitude, *take_log=True*,convert_function=_ConvertAccel, units=r"\rm{cm}/\rm{s}^{2}") def _RadiationForceMagnitude(field, data): return ( data["RadiationAccelerationMagnitude"] * data["Density"] * data["CellVolume"]) add_field("RadiationForceMagnitude", function=_RadiationForceMagnitude, * take_log=True*, units=r"\rm{dynes}") before the stars switch on when the radiation acceleration baryon fields are all 0.0 everywhere I get the following error: Traceback (most recent call last): File "MultiPlotProj.py", line 65, in <module> s = pc.add_projection("RadiationForceMagnitude", ax, weight_field="Density", figure=fig, axes=axes[0][3], use_colorbar=False) File "/home/h-clark/YT/src/yt-hg/yt/visualization/plot_collection.py", line 742, in add_projection size=fig_size, periodic=periodic)) File "/home/h-clark/YT/src/yt-hg/yt/visualization/plot_types.py", line 310, in __init__ self.__init_temp_image(use_colorbar) File "/home/h-clark/YT/src/yt-hg/yt/visualization/plot_types.py", line 347, in __init_temp_image self.set_width(1,'unitary') File "/home/h-clark/YT/src/yt-hg/yt/visualization/plot_types.py", line 436, in set_width self._refresh_display_width() File "/home/h-clark/YT/src/yt-hg/yt/visualization/plot_types.py", line 454, in _refresh_display_width self._redraw_image() File "/home/h-clark/YT/src/yt-hg/yt/visualization/plot_types.py", line 384, in _redraw_image newmin = na.nanmin(buff[bI]) File "/home/h-clark/YT/lib/python2.6/site-packages/numpy/lib/function_base.py", line 1494, in nanmin return _nanop(np.min, np.inf, a, axis) File "/home/h-clark/YT/lib/python2.6/site-packages/numpy/lib/function_base.py", line 1355, in _nanop res = op(y, axis=axis) File "/home/h-clark/YT/lib/python2.6/site-packages/numpy/core/fromnumeric.py", line 1829, in amin return amin(axis, out) ValueError: zero-size array to ufunc.reduce without identity Is there a way to set it so I get a log scale when plotting projections that does not break when the fields are all zero? Many thanks, Libby -- Elizabeth Harper-Clark MA MSci PhD Candidate, Canadian Institute for Theoretical Astrophysics, UofT Sciences and Engineering Coordinator, Teaching Assistants' Training Program, UofT www.astro.utoronto.ca/~h-clark http://www.astro.utoronto.ca/%7Eh-clark h-clark@cita.utoronto.ca Astronomy office phone: +1-416-978-5759