Figure 1

Scree test for the Ross et al dataset. Eigenvalues from the 60 × 60 cell line correlation matrix showed that, beginning with the break in the plot after component 9, a straight scree line could be fitted to the remaining values. Such a finding suggests that the eigenvalues after component 9 represent only error variance. The term "scree" was borrowed from geology where it refers to debris (i.e. error) that has fallen to the base of a mountain. Note that for clarity of presentation, the first eigenvalue of 13.787 was not plotted.