Hello all, I looked through the previous threads on yt-users, and I don't see this particular problem described. Hoping for some help. So, the quantity dark_matter_density is a CIC-deposited particle quantity, which becomes a grid field. I would like to do something like this: for every grid voxel, calculate the mean dm particle *velocity* inside that voxel return as a grid field Is that simple using CIC_deposit? The only mean particle velocity I've seen used in yt/enzo before is the one calculated for halos, by using HOP or FOF identification. thanks! Eric