How to add labels on axis in ternary diagram using ggtern package?

Question

The ternary diagram is shown in the following image. I want to add the labels of Z=60, Z=90 and Y=60 using ggtern package in R.

The R code link is the R code of ternary diagram

Answer 1

This is not the perfect answer, but I tried to achieve your wanted result with annotate like this:

ggtern(data=DATA,aes(x,y,z)) + 
  geom_polygon(aes(fill=Series),alpha=.5,color="black",size=0.25) +
  scale_fill_manual(values=as.character(unique(DATA$Series))) +
  theme(legend.position=c(0,1),legend.justification=c(0,1)) + 
  labs(fill="Region",title="Sample Filled Regions") +
  annotate(geom  = 'text',
           x     = c(0.1, 1/3, 0.0),
           y     = c(0.0, 0.0, 1.5),
           z     = c(0.5, 1/3, 1.0),
           angle = c(0, 0, 0),
           vjust = c(2.5, 2.5, -1.5),
           hjust = c(0.0, -0.2, 0.0),
           label = c("Z=90","Z=60","Y=60"),
           color = c("black","gray",'orange')) + # for inspection
  theme_nomask()   # allows drawing beyond the borders 

This yields the following picture: