In ggHoriPlot,geom_horizon will create fill Categories ypos3 .. yneg1 ..yneg13 ,refer to the legend in attached image.

How to understand Categories and it’s created according what kind of logic ？ Thanks!

library(tidyverse)
library(ggHoriPlot)
fc <- COVID$countriesAndTerritories %>% unique() %>% head(30)
COVID %>% filter(countriesAndTerritories %in% fc ) %>% ggplot(aes(x=date_mine,y=y))+
  facet_grid(countriesAndTerritories~.)+
  geom_horizon()+
  scale_fill_hcl(reverse = TRUE)