Figure 8: The PCA results for 479 galaxies from ALFALFA, SDSS, and 2MASS with colors. Here we only show the strongest ones, PC1 and PC2, because other principal components are not significant by PCA criterions. PC1 is well correlated with all the variables. The color is correlated with other variables and PC1 in the first row as well as strongly correlated with PC2 as in Figure 6. In this plot, and .