Dear all, I tried the following defination of Particle Velocity Magnitude without bulk velocity correction. def _ParticleVelocityMagnitudenoBVcor(field, data): return ( data["particle_velocity_x"]**2.0 + \ data["particle_velocity_y"]**2.0 + \ data["particle_velocity_z"]**2.0 )**(1.0/2.0) add_field("ParticleVelocityMagnitudenoBVcor", function=_ParticleVelocityMagnitudenoBVcor, take_log=False, units=r"\rm{cm/s}" ) and tried to calculate the weighted average value of it with the following line vrms_dm_no_bv_cor = sphere.quantities["WeightedAverageQuantity"]("ParticleVelocityMagnitudenoBVcor", "ParticleMass") But I am getting the following error IndexError: too many indices for array What could be the reason? How can I compute Particle Velocity Magnitude without bulk velocity correction? Thanks -- Reju Sam John