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,  14:05, 14 February 2008
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== Definitions ==

== Definitions ==

=== Data quality indicators ===

=== Data quality indicators ===
* R<sub>sym</sub> and R<sub>merge</sub> : the formula is
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* R<sub>sym</sub> and R<sub>merge</sub> : the formula for both is

$[itex] R_{merge} = \frac{\sum_{hkl}\vert I_{hkl}-\langle I_{hkl}\rangle\vert}{\sum_{hkl}I_{hkl}} + R = \frac{\sum_{hkl}\vert I_{hkl}-\langle I_{hkl}\rangle\vert}{\sum_{hkl}I_{hkl}}$
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$− R=\frac{\sum_{hkl_{unique}}\vert F_{hkl}^{(obs)}-F_{hkl}^{(calc)}\vert}{\sum_{hkl_{unique}} F_{hkl}^{(obs)}}$

[/itex]
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<br>
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<br>
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where $\langle I_{hkl}\rangle$ is the average of symmetry- (or Friedel-) related observations of a unique reflection, and the summation is over all observations, leaving out those that have no symmetry mates (or Friedel) in the dataset.

* Redundancy-independant version of the above: R<sub>meas</sub>

* Redundancy-independant version of the above: R<sub>meas</sub>

* measuring quality of averaged intensities/amplitudes: R<sub>p.i.m.</sub> and R<sub>mrgd-F</sub>

* measuring quality of averaged intensities/amplitudes: R<sub>p.i.m.</sub> and R<sub>mrgd-F</sub>

=== Model quality indicators ===

=== Model quality indicators ===
* R and R<sub>free</sub> : the formula is (LaTex please )
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* R and R<sub>free</sub> : the formula for both is

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$+ R=\frac{\sum_{hkl_{unique}}\vert F_{hkl}^{(obs)}-F_{hkl}^{(calc)}\vert}{\sum_{hkl_{unique}} F_{hkl}^{(obs)}} +$
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<br>
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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? ==

== what do R-factors try to measure, and how to interpret their values? ==

* relative deviation of

* relative deviation of
1,313

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