Correspondence Analysis and Kriging: Projection of Quantitative Information on the Factorial Maps

In this study, a methodological scheme is proposed for the combined use of Analyse Factorielle des Correspondances—AFC (or Correspondence Analysis) and the Ordinary Kriging method to display values of quantitative variables as supplementary points (or as “supplementary data”) onto the factorial maps (or planes) resulting from the application of AFC to a contingency table of two categorical variables. The proposed method can also be generalized in the case of Multiple Correspondence Analysis (Analyse des Correspondances Multiples). The kriging method is widely used as one of the most effective spatial interpolation techniques. The proposed methodological scheme is demonstrated using hypothetical data from a 5 \(\times \) 4 contingency table (sites\(\times \)crops). Fertilizer mean costs will be used as supplementary points or “supplementary data”. Also, a specific data coding scheme is proposed aiming at a better presentation and interpretation of the graphical results.