Hydrogen bonding continued trans-bonded

Indicator variables have also been used to account for other struetural features, e.g. for intramolecular hydrogen bonds, hydrogen bond donor and acceptor properties, ortho effects, cis/trans isomerism, different parent skeletons, different test models, etc. [22, 390]. Some precautions are necessary indicator variables should not describe a single compound (in this case the corresponding group contribution includes the experimental error of this one biological activity value) and the use of indicator variables should be justified from a theoretical point of view otherwise, continuous variables will be mixed with meaningless dummy variables, just to fit the data. 

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