在 ggplot2 错误中添加区域外的文本 plot

Question

I'm trying to add text outside area plot like this

I tried

ggplot(data=df, aes(y=Latitude, x=Longitude)) +
    geom_raster(aes(fill=PM10)) +
    scale_y_continuous(breaks = c(-10,-5,0,5), labels = c("10S","5S","0","5N"),
                       expand = c(0,0)) + 
    scale_x_continuous(breaks =c(100,120,140),labels = c("100E","120E","140E"),
                       expand = c(0,0)) +
    ggtitle(expression("Konsentrasi Aerosol PM"[10])) +
    theme(plot.title = element_text(hjust = 0.5)) +
    scale_fill_gradientn(parse(text="PM10 (μg/m^3)"),colours=warna) +
    geom_path(data = shapefile_df, aes(x = long, y = lat, group = group),
              color = 'black', fill= "gray") +
    annotate("text", x = 98.5, y=6.6, label = "2020-04-01  12:00 WITA") +
    annotate("text", x = 98.5, y=-11.6, label = "Waktu Validasi: 2020-04-01  12:00 WITA")

But I got

then i trying to use cowplot

kiri_atas <- as.data.frame("2020-04-01  12:00 WITA")
ann <- ggplot(kiri_atas, aes(x = 0, y = 0, label =kiri_atas)) +
    geom_text() +
    theme_void()

  plot_grid(ann, a, ncol = 1, rel_heights = c(.05, 1), align = 'v')

I got

I try to use gtable

a <-  ggplot(data=df, aes(y=Latitude, x=Longitude)) +
    geom_raster(aes(fill=PM10)) +
    scale_y_continuous(breaks = c(-10,-5,0,5), labels = c("10S","5S","0","5N"),
                       expand = c(0,0)) + 
    scale_x_continuous(breaks =c(100,120,140),labels = c("100E","120E","140E"),
                       expand = c(0,0)) +
    ggtitle(expression("Konsentrasi Aerosol PM"[10])) +
    theme(plot.title = element_text(hjust = 0.5)) +
    scale_fill_gradientn(parse(text="PM10 (μg/m^3)"),colours=warna) +
    geom_path(data = shapefile_df, aes(x = long, y = lat, group = group),
              color = 'black', fill= "gray")
a = gtable_add_grob(a, grobTree(textGrob("left", x=0, hjust=0), 
                                textGrob("right", x=1, hjust=1)), 
                    t=1, l=4)

grid.draw(a)

Nothing happens, pls help me to solve this how to add text like first picture in topleft, topright, bottomleft, bottomright? And get Title in center and bold?

Answer 1

Just a quick answer, but you can try adding something like a subtitle and caption, for some of the text. I got the information from here: https://www.datanovia.com/en/blog/ggplot-title-subtitle-and-caption/

ggplot(data=df, aes(y=Latitude, x=Longitude)) +
    geom_raster(aes(fill=PM10)) +
    scale_y_continuous(breaks = c(-10,-5,0,5), labels = c("10S","5S","0","5N"),
                       expand = c(0,0)) + 
    scale_x_continuous(breaks =c(100,120,140),labels = c("100E","120E","140E"),
                       expand = c(0,0)) +
    theme(plot.title = element_text(hjust = 0.5)) +
    scale_fill_gradientn(parse(text="PM10 (μg/m^3)"),colours=warna) +
    geom_path(data = shapefile_df, aes(x = long, y = lat, group = group),
              color = 'black', fill= "gray") +
    labs(title = "title",
              subtitle = "subtitle",
              caption = "caption")