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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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<math>
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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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</math>
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for amplitudes, and analogously for intensities:
    
=== Model quality indicators ===
 
=== Model quality indicators ===
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<br>
 
<br>
 
where <math>F_{hkl}^{obs}</math> and <math>F_{hkl}^{calc}</math> 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 <math>F_{hkl}^{obs}</math> and <math>F_{hkl}^{calc}</math> 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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