Hi, I want to write a script in yt that reads in data from a simulation output, extracts a 3-dimensional grid from it of a set size at a fixed resolution and then iterate through the data points calculating various properties. I think I can do this using covering_grid using the example in the cookbook: cube = pf.h.covering_grid(4, left_edge=[16.4299, 10.8963, 16.0], right_edge=[18.4299, 12.8963, 16.02], dims=[258,258,4], fields=["PotentialField"]) But I'm now not sure how to get to the data! I'd like to write a loop in the form: k = 0, 3 j=0, 257 i = 0, 257 something = data(i,j,k)*etc I feel this should be obvious but I can't figure out the AMRCoveringGrid object! Thanks, Elizabeth