DeltaCC12

ΔCC_1/2 is a quantity, that detects datasets/frames, that are non-isomorphous. As described in 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, but is not influenced by a random number sequence as shown in 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]\displaystyle{ \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}- that means if omitting dataset i from calculations, a lower CC_1/2 results, which is why we want to keep it. Thus 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} - that 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.