# Xds nonisomorphism

xds_nonisomorphism[1] is a program that clusters datasets as stored in their unmerged reflection file (typically called XDS_ASCII.HKL) as written by XDS. It implements the method of Brehm and Diederichs (2014) and theory of Diederichs (2017).

This program determines the lengths of the vectors from the CC1/2 of the data sets, and the angles between vectors from the correlation coefficients between data sets. It requires data sets with internal multiplicity, and mutual overlap. Angles are expressed in degrees. Less than 10° should be considered good isomorphism, 90° means completely unrelated (i.e. non-isomorphous) datasets (theoretically, higher angles are also possible if data sets are anti-correlated). After the analysis, it produces a 3D representation of the arrangement of data sets such that the distances in 3D try to reproduce the angles - please note that this is a completely different representation from that of xscale_isocluster! xds_nonisomorphism prints a short help text if the -h option is used.