Figure 2
From: Protein structure similarity from principle component correlation analysis
(a) The plot of scaled λ2 (the second largest eigenvalue) versus λ1 (the maximum eigenvalue), calculated using the PD matrix, for all proteins in the four data sets, and (b) the plot of λ1 of PID matrix versus that of PD matrices. The symbol representations are: ○ – structure set I; ▽ – set II; 
– set III; □ – set IV; ☍ – set V; and 
– set VI.