Not purely a ccp4 question, but an MTZ file is involved, so stick with me. I've collected a SAD data set, and processed with XDS. I can use XDSCONV to generate an MTZ, SHELX, and CNS file. I chose the MTZ file since it keeps the intensities. SHELX does too (the F**2), but has separate lines for (h,k,l) and (-h,-k,-l). The MTZ file has hkl,IMEAN, SIGIMEAN, I+, SIGI+, I-, SIGI-.
I used mtzdump (or could use MTZVARIOUS) to convert this file to a simple ASCII file, and then extracted just the hkl, I+, SIGI+, I-, SIGI-. Since CCP4 fills in all of the reflections in an ASU, I removed those reflection entries with SIGIMEAN = -999.0. I have a file with has some entries with -999 (for the non-measured value), especially those in the centric zones. For SOLVE, does it identify entries with a value of -999 as a placeholder, or should I entirely removed those from the data file? I used the options PREMERGED READFORMATTED READ_INTENSITIES in SOLVE. What if I measured I- but I+? That's why I left them all in. Suggestions on what is best for the solve run? I'm concerned that it's interpretting the -999 as a real measurement. Bernie Santarsiero
