supporting add label for each slice of pie

label_radius 控制标签的位置，相对饼图的半径
label_show_ratio 控制标签是比例，还是原始值，默认为TRUE是比例.
label_threshold 为了防止一些较小比例值出现重叠，引入该参数，如果比例小于该值，则不展示

> library(ggplot2)
> library(scatterpie)
> d <- data.frame(x=rnorm(5), y=rnorm(5))
> d$A <- abs(rnorm(5, sd=1))
> d$B <- abs(rnorm(5, sd=2))
> d$C <- abs(rnorm(5, sd=3))
> ggplot() +
  geom_scatterpie(
    aes(x=x, y=y), data = d, cols=c("A", "B", "C"),
    label_radius=1.05
  ) +
  coord_fixed()

> d <- tidyr::gather(d, key="letters", value="value", -x:-y)
> d |> dplyr::select(c(x, y)) |> dplyr::distinct() |> dplyr::mutate(Cell=c('A','A','B','C','B')) -> d2
> d |> dplyr::left_join(d2) -> d3
Joining with `by = join_by(x, y)`
> d3$r_size <- c(2, 3, 4, 5, 6) * .01
> p4 <- ggplot() +
        geom_scatterpie(data = d3,
                        mapping = aes(x, y = y, r = r_size),
                        cols = 'letters',
                        long_format = TRUE,
                        label_radius = 1.1,
                        label_show_ratio = FALSE,
                        label_threshold = 0.06,
                        fontsize = 3
        ) +
        coord_fixed()
> p4

YuLab-SMU / scatterpie

supporting add label for each slice of pie #49