Finding the Appropriate Descriptor

According to the previous definition, molecular descriptors represent properties of a molecule. The most important issue is to eliminate properties that are not relevant for the task to be solved. This is similar to analytical methodology, where unwanted effects are eliminated or suppressed by using chemical or physical methods, like chemical modifiers in chromatography or background compensation in spectroscopy. 

Finding the appropriate descriptor for the representation of chemical structures is one of the basic problems in chemical data analysis. Several methods have been developed for the description of molecules, including their chemical or physicochemical properties [42]. 

The wide variety of molecular structures usually requires a reduction of information together with the encoding process. Additionally, structural features should be encoded including properties that have a profound influence on the features to be investigated, such as molecular symmetry, physicochemical bond, or atomic or molecular properties like charge distribution, electronegativity, and polarizability of the compounds. Radial distribution functions and their derivatives have been found 

The next chapter deals with the development and modifications of RDF descriptors. 

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