This analysis is new to Prism 7. Its purpose is to make it easier to transform X values that are concentrations.

Special handling of X=0

Why handle X=0 specially? Because it is common to transform X values to their logarithms, which is required before fitting some models to your data. Since the logarithm of zero is undefined, if you enter X=0 that value will be empty (missing) after transformation. This analysis  lets you substitute some other value (a tiny concentration) for zero before taking the logarithm. For example if your data go from 10-9 to 10-3 molar and you plan to take the logarithm, consider changing the 0 value to 10-11.

Change units

Multiply or divide all X values by a constant you select to change units.

Transform to logarithms

Choose whether you want to use natural logarithms or base10 common logarithms. Unless you are a mathematician, you may only know about common logarithms and "natural logarithms" will seem very unnatural.