DeltaCC12: Difference between revisions

ΔCC_1/2 is a quantity that detects datasets/frames which are non-isomorphous. As described in [https://scripts.iucr.org/cgi-bin/paper?zw5005 Assmann and Diederichs (2016)], ΔCC_1/2 is calculated with the σ-τ method. This method is a way to calculate the Pearson correlation coefficient for the special case of two sets of values (intensities) that randomly deviate from their true values. The σ-τ method is not influenced by a random number sequence as shown in [https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3457925/ Karplus and Diederichs (2012)]. For the σ-τ method CC_1/2 is calculated for all datasets/frames, which will be called CC_{1/2_overall} and CC_1/2 is calculated for all datasets/frames except for one dataset i, which is omitted from calculations and denoted as CC_{1/2_i}. The difference of the two quantities is ΔCC_1/2.

: <math>\Delta CC_{1/2}= CC_{1/2 overall}-CC_{1/2_i} </math>

If ΔCC_1/2 is > 0 (CC_{1/2_overall} is bigger than CC_{1/2_i}) it means that by omitting dataset i from calculations a lower CC_1/2 results. As we want to maximize CC_1/2 the dataset is kept for calculations, it is improving the whole merged dataset. If Δ CC_1/2 is < 0 (CC_{1/2_overall} is smaller than CC_{1/2_i}) it means that by omitting dataset i from calculations a higher CC_1/2 results, which is why we want to exclude it from calculations, because it is impairing the whole merged dataset.  

The ΔCC_1/2  method is applicable for single frames, SSX data and SFX data. ΔCC_1/2 can be calculated by [[XDSCC12]].