Topographical indices

Randic, M. and Razinger, M. (1995a). Molecular Topographic Indices. J.Chem.Inf.Comput.ScL, 35,140-147. 

The number of topological and topographical indices increases each month, with recent additions including new shape descriptors [59], descriptors based on graph valence shells [60], and a descriptor based on topological distance counts [61], The latter is shown to be easier to compute while giving results at least as good as the CoMFA and EVA descriptors mentioned below. 

In QSAR and QSPR studies, the standard ways of removing redundancy from large numbers of topological and topographical indices include principal component analysis, chi-squared analysis, and multiple regression analysis (MRA). Most QSAR and QSPR applications deal with very small datasets, and so the dimensionality does not cause a problem for PCA or chi-squared analysis. MRA does not impose any restrictions on the type and number of descriptors. The selection process is based on two principles, namely, to cover as much of parametric space as possible (principle of variance) while choosing independent descriptors (principle of orthogonality). 

Randic M, Razinger M. Molecular topographic indices. J Chem Inf Comput Sci 1995 35 140-147. 

Topological and topographical indices In QSP/AR, this class of descriptors is extensively used by chemists. Extensive literature on the subject exists, and many novel indices are still being introduced. Among the classic ones, the Wiener index is best known.This index is... 

Mathematical representation of a structure allows one to extract from a structure a number of mathematical invariants, quantities that do not depend on assumed labeling of atoms in the structure. One refers to structural invariants as topological or topographic indices if they reflect upon the molecular connectivity or molecular geometry, respectively. The former are based on a graph as a model for a molecule. Hence, correctly these invariants should have been called graph theoretical indices. However, the label topological index prevailed. 

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