autoplot - How to adjust loading labels?

Question

I would like to be able to adjust the positions of the loading labels, so that they do not fall atop the the arrows. However, I do not know where the adjustments need to be made. The geom_text can be used to adjust the position of the site positions, but I cannot find where the vectors are stored in str(g).

library(ggplot2)
library(ggfortify)
df <- data.frame(replicate(10,sample(-10:10,10,rep=TRUE)))
names(df) <- c('up','down','left','right','circle','square','triangle','x','r1','l1')
rownames(df) <- paste('Dummy Site', seq(0,9,1))
g <- autoplot(prcomp(df[,-11], scale=TRUE), data=df,
              loadings.label=TRUE, loadings=TRUE, 
              loadings.label.size=8, loadings.colour='blue',
              label.size=5) +
     geom_text(vjust=-1, label=rownames(df)) +
     theme(plot.background=element_blank(),
           panel.background=element_rect(fill='transparent',color='black',size=1),
           legend.text=element_text(hjust=1),
           legend.key=element_blank()) 
g

I've looked in ggplot2::theme and I've examined the help docs for autoplot, but can't find any mention of the adjusting label position. Bonus points if it can adjust based on the vector of the arrow, but a static adjustment would be acceptable.

Currently, here is what the plot looks like:

Answer 1

You can get the coordinates by layer_data(g, 2). But autoplot(prcomp.obj) passes other arguments to ggbiplot(), so you can change label and loadings.label position using arguments of ggbiplot(), such as loadings.label.hjust (see ?ggbiplot).

example code:

arrow_ends <- layer_data(g, 2)[,c(2,4)]

autoplot(prcomp(df[,-11], scale=TRUE), data=df,
         loadings.label=TRUE, loadings=TRUE, 
         loadings.label.size=8, loadings.colour='blue',
         label.size=5, loadings.label.vjust = 1.2) +     # change loadings.label position
     geom_point(data = arrow_ends, aes(xend, yend), size = 3) +  # the coordinates from layer_data(...)
     geom_text(vjust=-1, label=rownames(df)) +
     theme(plot.background=element_blank(),
           panel.background=element_rect(fill='transparent',color='black',size=1),
           legend.text=element_text(hjust=1),
           legend.key=element_blank())