Dear Ralf, dear all,

Recently there was some discussion about reading of XDS output files here on PhenixBB, and I'd like to try and shed some light on this.

First, I'm glad to hear this is possible in principle! However, the caveat is, that three types of "native" output files are written by programs from the "XDS program package":

a) the main program ("xds", or "xds_par") writes only one type of file, called XDS_ASCII.HKL. This has _unmerged_ observations, and this is therefore currently _unsuitable_ for reading by Phenix programs (since the Phenix routine expects merged, unique reflections). If this is nevertheless tried, I see the danger that Phenix might "eat" all observations of a unique reflections except one, possibly without telling about this problem (? - I didn't try!!) - this is definitely not what you want!
b) the program "xscale" can write an output file with unmerged observations. This is the default, and corresponds to MERGE=FALSE in XSCALE.INP . As for a), this is also not what you want!
c) the program "xscale" can write an output file with merged observations. This is not the default, but can be obtained by using MERGE=TRUE in XSCALE.INP . This is what you want to read with Phenix programs.

Thus only possibility c) will give you a "native XDS" file that is ready to be read by Phenix programs.

In addition to this possibility, one can use of course use "xdsconv" to go from XDS_ASCII.HKL (or any file written by "xscale") to a (non-native XDS) filetype that Phenix programs can read. The most general should be to write a MTZ file, but CNS/X-PLOR type files can also be produced.

If someone would implement merging of observations in the Phenix routines (it should be straightforward: negative sigmas indicate that observations should not be used; otherwise the standard formulas could be used; symmetry-related reflections of course have to be handled correctly but they are already sorted by unique reflection), then possibilities a) and b) would also work. But until this is implemented, c) should be used.

Hope this helps,

Kay

P.S. The filetypes and everything else around XDS is accurately documented at http://www.mpimf-heidelberg.mpg.de/~kabsch/xds/
--
Kay Diederichs                http://strucbio.biologie.uni-konstanz.de
email: [email protected]    Tel +49 7531 88 4049 Fax 3183
Fachbereich Biologie, Universit�t Konstanz, Box M647, D-78457 Konstanz

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