Improving positioning of map / polygon labels-CodePudding

The

plot(xy.sp) polygonsLabel(xy.sp, "L\na\nb\ne\nl")

plot(xy.sp) polygonsLabel(xy.sp, "MY TEST LABEL\n\n TWO LINES HIGH")

CodePudding user response：

Using what you've got along with the information that @Henrik provided, this works pretty well.

There is a catch, though. ggplot text to plot sizing is not scaled uniformly. Are you using this in the viewer pane? Are you exporting this? What sizes are you using? For example, the title might be a font size of 15 at 300 dpi, but if you wanted to add text of the same size, you would have to set the size to 15/.pt (where .pt is a static value from the package ggplot2).

Additionally, the default font type in ggplot is not monospaced—every letter doesn't get the same amount of real estate (like courier, for example).

Check out these plots which have been saved at 300dpi, 3in x 3in, with the text size = 12/.pt and coord_equal. In the first plot "HHH" takes just over .25 units on the x-axis. In the second, it takes 1.5 units. In the last plot, it takes just over 1/2 unit.

This works. However, without a set scaling mechanism, it still requires manual intervention regarding either the font size or the string wrapping.

library(polylabelr) library(stringr) library(tidyverse) poly_foo <- data.frame(x = c(0:1, rep(2,4), rep(1.5,3), 0), y = c(rep(0,3), 1:3, 3:1, 1)) p <- ggplot(poly_foo, aes(x, y) ) geom_polygon(color = "black", fill = NA) plr <- poi(poly_foo, precision, = .1) p coord_equal() annotate("text", x = plr$x, y = plr$y, label = "How about here?" %>% str_wrap(., width = 9/(plr$dist * 2))) pf2 <- mutate(poly_foo, x = x * 2, y = y^2) poi2 <- poi(pf2, precision = .1) ggplot(pf2, aes(x, y) ) geom_polygon(color = "black", fill = NA) coord_equal() annotate("text", x = poi2$x, y = poi2$y, label = "Intuitive enough?" %>% str_wrap(., width = 9/(poi2$dist * 2))) pf3 <- mutate(poly_foo, x = x^2, y = y 4) poi3 <- poi(pf3, precision = .1) ggplot(pf3, aes(x, y) ) geom_polygon(color = "black", fill = NA) coord_equal() annotate("text", x = poi3$x, y = poi3$y, label = "Intuitive enough?" %>% str_wrap(., width = 9/(poi3$dist * 2))) pf4 <- mutate(poly_foo, x = x^1/2, y = y^(1/3)) poi4 <- poi(pf4, precision = .1) ggplot(pf4, aes(x, y) ) geom_polygon(color = "black", fill = NA) coord_fixed() annotate("text", x = poi4$x, y = poi4$y, label = "Intuitive enough?" %>% str_wrap(., width = 9/(poi4$dist * 2)))