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R-factors: Difference between revisions
→Definitions
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=== Comparing two sets of structure factor amplitudes or intensities === | === Comparing two sets of structure factor amplitudes or intensities === | ||
The following is symmetric, and suitable for comparing two data sets, or two model amplitudes: | The following is symmetric, and suitable for comparing two data sets, or two model amplitudes: | ||
: <math> | |||
R_{scale}=\frac{\sum_{hkl}\vert F_{hkl,i}-F_{hkl,j}\vert}{0.5\sum_{hkl} F_{hkl,i}+F_{hkl,j}} | |||
</math> | |||
for amplitudes, and analogously for intensities. | for amplitudes, and analogously for intensities. | ||
=== Model quality indicators === | === Model quality indicators === | ||
* R and [[iucr:Free_R_factor|R<sub>free</sub>]] : the formula for both is | * R and [[iucr:Free_R_factor|R<sub>free</sub>]] : the formula for both is | ||
: <math> | |||
R=\frac{\sum_{hkl}\vert F_{hkl}^{obs}-F_{hkl}^{calc}\vert}{\sum_{hkl} F_{hkl}^{obs}} | |||
</math> | |||
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]]. | ||