Is it possible to change the type of lines of the normal probability ellipsoids in ggbiplot, e.g. have them dashed and dotted lines instead of or additional to the different colors? I couldn't find anything in the documentation of ggbiplot except this to be used as MWE:
library(ggbiplot)
data(wine)
wine.pca <- prcomp(wine, scale. = TRUE)
print(ggbiplot(wine.pca, obs.scale = 1, var.scale = 1, groups = wine.class, ellipse = TRUE, circle = TRUE))
To the best of my knowledge it isn't possible with any or the arguments passed to ggbiplot. Luckily ggbiplot is a pretty simple wrapper for some ggplot2 commands and data massaging. You can copy the source code make a custom function and change line 124 of the original source from:
g <- g + geom_path(data = ell, aes(color = groups, group = groups))
to:
g <- g + geom_path(data = ell, aes(color = groups, group = groups, linetype = groups))
Because of the plot scale it's hard to tell the lines apart without changing the size outside of the aes() statement.