# Changes

,  07:47, 14 October 2014
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To my knowledge, the only program that implements this currently (December 2008) is [[xds:XDSSTAT|XDSSTAT]].

To my knowledge, the only program that implements this currently (December 2008) is [[xds:XDSSTAT|XDSSTAT]].
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=== Comparing two sets of structure factor amplitudes or intensities ===
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The following is symmetric, and suitable for comparing two data sets, or two model amplitudes:
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$+ R=\frac{\sum_{hkl}\vert F_{hkl}^{i}-F_{hkl}^{j}\vert}{\sum_{hkl} 1/2 (F_{hkl}^{i}+F_{hkl}^{j})} +$
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for amplitudes, and analogously for intensities:

=== Model quality indicators ===

=== Model quality indicators ===
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<br>

<br>

where $F_{hkl}^{obs}$ and $F_{hkl}^{calc}$ have to be scaled w.r.t. each other. R and R<sub>free</sub> differ in the set of reflections they are calculated from: R is calculated for the [[working set]], whereas R<sub>free</sub> is calculated for the [[test set]].

where $F_{hkl}^{obs}$ and $F_{hkl}^{calc}$ have to be scaled w.r.t. each other. R and R<sub>free</sub> differ in the set of reflections they are calculated from: R is calculated for the [[working set]], whereas R<sub>free</sub> is calculated for the [[test set]].
== what do R-factors try to measure, and how to interpret their values? ==
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* relative deviation of
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=== Data quality ===
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* typical values: ...
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=== Model quality ===
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==== Relation between R and R<sub>free</sub> as a function of resolution ====

==== Relation between R and R<sub>free</sub> as a function of resolution ====
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