Reindexing

For some background, see reindexing

Reindexing within XDS is a final step that might have to be done in order to make the reduced data consistent with another existing dataset, or an atomic model.

Possible reindexing operators are listed at the bottom of IDXREF.LP FIXME: insert example here if the IDXREF step is run in the correct spacegroup. These operators (usually there's only one) are then applied in the CORRECT step, using the REIDX= keyword and the 12 numbers given.

Thus there are two possible strategies for XDS data reduction:

1. to use SPACE_GROUP_NUMBER=0 up to and including INTEGRATE, and to use CORRECT to decide upon the spacegroup using the REIDX= operators from the table in IDXREF.LP.
2. to use the known SPACE_GROUP_NUMBER for IDXREF and INTEGRATE.

The connection between the two philosophies is by doing optimization: the first pass through the data is done to determine the space group (JOB=XYCORR INIT COLSPOT IDXREF DEFPIX INTEGRATE CORRECT). Then the optimization is performed (JOB=INTEGRATE CORRECT). After this, one obtains possible reindexing operators (JOB=IDXREF), which may then be tested (JOB=CORRECT).