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Optimisation: Difference between revisions
→Wilson outliers (aliens)
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* True outliers should be put (i.e. copied) into REMOVE.HKL, and [[CORRECT]] then should be re-run.<br /> My personal rule of thumb is that when the integer parts of Z ("int(Z)") are the numbers 8, 9, ... n, but there are no aliens (or just a single one) with int(Z) = n+1, then I consider all aliens with Z > n+1 as outliers. <br /> A different rule of thumb would be to simply consider aliens with Z of 20 or more as outliers - this is the default since January 2010 (the cutoff may be modified with the REJECT_ALIEN keyword). | * True outliers should be put (i.e. copied) into REMOVE.HKL, and [[CORRECT]] then should be re-run.<br /> My personal rule of thumb is that when the integer parts of Z ("int(Z)") are the numbers 8, 9, ... n, but there are no aliens (or just a single one) with int(Z) = n+1, then I consider all aliens with Z > n+1 as outliers. <br /> A different rule of thumb would be to simply consider aliens with Z of 20 or more as outliers - this is the default since January 2010 (the cutoff may be modified with the REJECT_ALIEN keyword). | ||
* Another way to judge Wilson outliers is to identify resolution ranges that deviate from 1. in the table '''HIGHER ORDER MOMENTS OF WILSON DISTRIBUTION OF ACENTRIC DATA''' in [[CORRECT.LP]]. "Aliens" that are put into REMOVE.HKL will lower the values in these resolution ranges! | * Another way to judge Wilson outliers is to identify resolution ranges that deviate from 1. in the table '''HIGHER ORDER MOMENTS OF WILSON DISTRIBUTION OF ACENTRIC DATA''' in [[CORRECT.LP]]. "Aliens" that are put into REMOVE.HKL will lower the values in these resolution ranges! | ||
* SCALEPACK users: don't confuse this process of rejecting Wilson outliers with the iterative procedure of rejecting scaling outliers that is usually done when using SCALEPACK. Scaling outliers are handled non-iteratively in [[XDS]]; the only way to influence [[XDS]] in this respect is by modifying [[WFAC1]]. | * SCALEPACK users: don't confuse this process of rejecting Wilson outliers with the iterative procedure of rejecting scaling outliers that is usually done when using SCALEPACK. Scaling outliers are handled non-iteratively in [[XDS]]; the only way to influence [[XDS]] in this respect is by modifying [[FAQ#reducing_WFAC1_below_its_default_of_1_improves_my_data.2C_right.3F|WFAC1]]. | ||
* if CORRECT rejects many "aliens" in a very weak high resolution shell because they have Z>20 then this is due to the fact that the reflections do not obey Wilson statistics. If this happens, the REJECT_ALIEN parameter should be set much higher (e.g. 100). | * if CORRECT rejects many "aliens" in a very weak high resolution shell because they have Z>20 then this is due to the fact that the reflections do not obey Wilson statistics. If this happens, the REJECT_ALIEN parameter should be set much higher (e.g. 100). | ||