Abstract: Based on the results obtained from projection pursuit, all cycloalkanes investigated show an interesting classification.Thus, a new variable named class distance variable of cycloalkane, which essentially describes information of branch, number of rings in the molecules and homologous series for cycloalkanes, is proposed.With the help of the new variable, both of fitting and prediction accuracy of the regression model can be dramatically improved.

Key words: Projection pursuit, QSPR, Cycloalkanes, Retention index