[R] Is it possible to get a downward pointing solid triangle plotting symbol in R?

[Rui Barradas]

Às 10:09 de 06/10/2023, Chris Evans via R-help escreveu:
> The reason I am asking is that I would like to mark areas on a plot 
> using geom_polygon() and aes(fill = variable) to fill various polygons 
> forming the background of a plot with different colours. Then I would 
> like to overlay that with points representing direction of change: 
> improved, no reliable change, deteriorated. The obvious symbols to use 
> for those three directions are an upward arrow, a circle or square and a 
> downward pointing arrow.  There is a solid upward point triangle symbol 
> in R (ph = 17) and there are both upward and downward pointing open 
> triangle symbols (pch 21 and 25) but to fill those with a solid colour 
> so they will be visible over the background requires that I use a fill 
> aesthetic and that gets me a mess with the legend as I will have used a 
> different fill mapping to fill the polygons.  This silly reprex shows 
> the issue I think.
> 
> library(tidyverse)
> tibble(x = 2:9, y = 2:9, c = c(rep("A", 5), rep("B", 3))) -> tmpTibPoints
> tibble(x = c(1, 5, 5, 1), y = c(1, 1, 5, 5), a = rep("a", 4)) -> 
> tmpTibArea1
> tibble(x = c(5, 10, 10, 5), y = c(1, 1, 5, 5), a = rep("b", 4)) -> 
> tmpTibArea2
> tibble(x = c(1, 5, 5, 1), y = c(5, 5, 10, 10), a = rep("c", 4)) -> 
> tmpTibArea3
> tibble(x = c(5, 10, 10, 5), y = c(5, 5, 10, 10), a = rep("d", 4)) -> 
> tmpTibArea4
> bind_rows(tmpTibArea1,
>            tmpTibArea2,
>            tmpTibArea3,
>            tmpTibArea4) -> tmpTibAreas
> ggplot(data = tmpTib,
>         aes(x = x, y = y)) +
>    geom_polygon(data = tmpTibAreas,
>                 aes(x = x, y = y, fill = a)) +
>    geom_point(data = tmpTibPoints,
>               aes(x = x, y = y, fill = c),
>               pch = 24,
>               size = 6)
> 
> Does anyone know a way to create a solid downward pointing symbol?  Or 
> another workaround?
> 
> TIA,
> 
> Chris
> 
Hello,

Maybe you can solve the problem with unicode characters.
See the two scale_*_manual at the end of the plot.



# Unicode characters for black up- and down-pointing characters
pts_shapes <- c("\U25B2", "\U25BC") |> setNames(c("A", "B"))
pts_colors <- c("blue", "red") |> setNames(c("A", "B"))

ggplot(data = tmpTibAreas,
        aes(x = x, y = y)) +
   geom_polygon(data = tmpTibAreas,
                aes(x = x, y = y, fill = a)) +
   geom_point(data = tmpTibPoints,
              aes(x = x, y = y, color = c, shape = c),
              size = 6) +
   scale_shape_manual(values = pts_shapes) +
   scale_color_manual(values = pts_colors)




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