[R] Presumably simple question about sorting/ordering

Hi, I'm stuck with a fairly basic re-ordering problem. I want to extract part of a matrix as a vector, and reorder it to match with an erratic sequence of x,y coordinates. Here's an example that shows what I want and how close I've got (but for some reason my mind just can't get the final

[R] image3d in misc3d

Hi, I'm trying to make sense of the image3d plots in misc3d. Unfortunately I can't find any authors on the help pages of the function to e-mail directly. In the following toy example, I'm puzzled as to why (1) the positions of the image plot on the axes include negative values when I think