**Figure 4:** Correlation and difference in percentage zeros seen with comparisons over time in the subjective groups. (a and b) Spearmanâ€™s correlation coefficient (r_{s}) was calculated from plots of metabolite concentrations determined from analysis done at two different time points.(a) Subsets 1 vs. 3, (b) Subsets 2 vs. 4. (c and d) Difference in percentage zeros between the two time points. (c) Subsets 1 vs. 3, (d) Subsets 2 vs.
4. The grey shaded area represents metabolites that are identified as difficult to quantify in all graphs: (a) and (b) r_{s}<0.8; (c) and (d) difference in percentage of zeros >10. The metabolites rated subjectively in Table 1 retain their grouping here. N/A is Not Analyzed. Error bars represent standard deviation of the values. |