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R-factors: Difference between revisions
→what kinds of problems exist with these indicators?
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* (R<sub>sym</sub> / R<sub>merge</sub> ) should not be used to judge [[data quality]], R<sub>meas</sub> should be used instead. The reason is that the former depend on multiplicity, whereas the latter doesn't. | * (R<sub>sym</sub> / R<sub>merge</sub> ) should not be used to judge [[data quality]], R<sub>meas</sub> should be used instead. The reason is that the former depend on multiplicity, whereas the latter doesn't. | ||
* R/R<sub>free</sub> and NCS: reflections in work and test set are not independent if chosen randomly. It is better to choose the test set reflections in thin resolution shells (FIXME: references and programs for this). A paper investigating this thoroughly is Fabiola, F., A. Korostelev, et al. (2006). "Bias in cross-validated free R | * R/R<sub>free</sub> and NCS: reflections in work and test set are not independent if chosen randomly. It is better to choose the test set reflections in thin resolution shells (FIXME: references and programs for this). A paper investigating this thoroughly is Fabiola, F., A. Korostelev, et al. (2006). "Bias in cross-validated free R factors: mitigation of the effects of non-crystallographic symmetry." Acta Cryst. D 62: 227-38. | ||
factors: mitigation of the effects of non-crystallographic symmetry." Acta | |||
* Sets of reflections used for calculating R<sub>free</sub> should be maintained throughout a project. This is nicely discussed at http://www.bmsc.washington.edu/people/merritt/xplor/rfree_example.html . | * Sets of reflections used for calculating R<sub>free</sub> should be maintained throughout a project. This is nicely discussed at http://www.bmsc.washington.edu/people/merritt/xplor/rfree_example.html . | ||