Hi, I just want to point out that for averaging maps (i.e. averaging between crystals instead of averaging within a single crystal as is usually done), the 2 maps to be averaged do not necessarily have the same distribution of density, the same density histogram, the same dynamic range if you prefer. Averaging 2 maps which do not have the same histograms without "real space scaling" by histogram matching (or mapping) can lead to map deterioration instead of map improvement. See the example given in Methods in Enzymology 277, pp18-53, the figure showing this is on pages 36-37. Fred. Stephen Graham wrote:
Hi there,
I'd like to average 2Fo-Fc maps from 2 (approximately) isomorphous data sets (one with ligand, one without) to see whether I get better density for some of the noisier bits of the structure. I don't want to do any kind of solvent flattening, histogram matching, cyclical averaging, etc; I just want to sum the equivalent pixels and divide by 2.
Is it possible to do this easily using any of the phenix tools? It seems like all the required plumbing is there with get_cc_mtz_mtz or superpose_maps, but I can't find a phenix utility for averaging two superposed maps.
Thanks,
Stephen