Figure 6

Global validation by correlation analysis of a combinatorial metabolite standard mixing GC/MS data set. The data matrix generated by MetabolomeExpress processing of the combinatorial standard mixing GC/MS data set (see Figure 3) was filtered to remove internal standards and analytes of unknown structure and then used to generate a correlation matrix which was used as input for hierarchical clustering in the statistical package, R. The reordered correlation matrix is shown as a heatmap with colours corresponding to analyte-analyte correlation coefficients (see color bar to the right). As expected, analytes were clustered into three major clusters corresponding to metabolite sub-mixes 1, 2 and 3 (see Figure 3). Analyte names have been coloured according to their metabolite submixture of origin (Mix 1 = red; Mix 2 = green; Mix 3 = blue). * Known breakdown product.