how to move tick marks and labels at right/left end of tiles in geom_tile ggplot?

Question

I am unable to move the x-axis labels, including tick marsk, in a geom_tile to the right end of each tile, I would also like to add the zero at the left end. I have tried breaks and labels but with no luck. Also using breaks and labels doesn't really work.

I am trying to achieve what is done in this answer but the solution suggested doens't work. How to force the x-axis tick marks to appear at the end of bar in heatmap graph?

my data

toplot=structure(list(year = c(125L, 250L, 375L, 500L, 625L, 750L, 875L, 
1000L, 1125L, 1250L, 125L, 250L, 375L, 500L, 625L, 750L, 875L, 
1000L, 1125L, 1250L, 125L, 250L, 375L, 500L, 625L, 750L, 875L, 
1000L, 1125L, 1250L, 125L, 250L, 375L, 500L, 625L, 750L, 875L, 
1000L, 1125L, 1250L, 125L, 250L, 375L, 500L, 625L, 750L, 875L, 
1000L, 1125L, 1250L, 125L, 250L, 375L, 500L, 625L, 750L, 875L, 
1000L, 1125L, 1250L, 125L, 250L, 375L, 500L, 625L, 750L, 875L, 
1000L, 1125L, 1250L, 125L, 250L, 375L, 500L, 625L, 750L, 875L, 
1000L, 1125L, 1250L), density = structure(c(1L, 1L, 1L, 1L, 1L, 
1L, 1L, 1L, 1L, 1L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 3L, 
3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 4L, 4L, 4L, 4L, 4L, 4L, 4L, 
4L, 4L, 4L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 2L, 2L, 2L, 
2L, 2L, 2L, 2L, 2L, 2L, 2L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 
3L, 4L, 4L, 4L, 4L, 4L, 4L, 4L, 4L, 4L, 4L), .Label = c("a", 
"b", "c", "d"), class = "factor"), value = c(-0.04, 
0.07, 0.01, -0.06, -0.05, 0.04, 0.13, 0.17, 0.19, 0.19, 0.02, 
0.27, 0.3, 0.3, 0.36, 0.35, 0.38, 0.5, 0.67, 0.77, -0.14, -0.08, 
-0.05, 0.18, 0.37, 0.4, 0.41, 0.44, 0.47, 0.73, -0.24, -0.73, 
-0.16, -0.06, -0.02, -0.04, -0.75, -0.74, -0.74, -0.74, -0.77, 
-0.17, -0.51, -0.57, -0.78, -0.79, -0.22, -0.21, -0.22, -0.73, 
-0.58, -0.53, -0.23, -0.24, -0.56, -0.25, -0.31, -0.34, -0.71, 
-0.42, -0.26, -0.25, -0.35, -0.34, -0.44, -0.44, -0.44, -0.45, 
-0.45, -0.45, -0.3, -0.44, -0.17, -0.18, -0.18, -0.18, -0.18, 
-0.48, -0.48, -0.48), type = structure(c(1L, 1L, 1L, 1L, 1L, 
1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 
1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 
1L, 1L, 1L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 
2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 
2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L), .Label = c("var1", 
"var2"), class = "factor")), .Names = c("year", "density", "value", 
"type"), row.names = c(NA, -80L), class = "data.frame")

my code

ggplot(toplot, aes(year, density)) + 
  geom_tile(aes(fill = value), colour = "black") + 
  scale_fill_gradientn(colours=c('#dc180a', 'orange', 'white', '#a0e100', '#2e7cff'),
                       values = rescale(c(-.5, 0, .8)), 
                       guide = "colorbar", limits = c(-.5, .8)) + 
  scale_x_continuous(breaks = seq(0, 1250, 250), expand = c(0, 0)) + 
  theme_bw(base_size = 20) + 
  theme(axis.text.x = element_text(), 
        axis.text.y = element_text(size = rel(1.1)),
        plot.title = element_text(hjust = 0.5)) + 
  facet_wrap(~type, ncol = 2) + 
  theme(strip.background = element_rect(fill = "#fafafa"))+ 
  theme(strip.text = element_text(colour = 'black'),
        panel.spacing = unit(1, "lines")) + 
  scale_y_discrete(expand = c(0, 0))

Answer 1

geom_raster() (a special case for geom_tile() accepts values for hjust and vjust, which controls the position of each tile relative to its coordinates. It doesn't appear to accept colour as an aesthetic for tile outlines, but you can fake it by placing grid lines (appropriately spaced) over the tiles:

ggplot(toplot, aes(x = year, y = density)) + 
  geom_raster(aes(fill = value), hjust = 0) + 
  geom_hline(yintercept = seq_along(toplot$density) + 0.5) +
  scale_fill_gradientn(colours=c('#dc180a', 'orange', 'white', '#a0e100', '#2e7cff'),
                       values = rescale(c(-.5, 0, .8)),
                       guide = "colorbar", limits = c(-.5, .8)) +
  scale_x_continuous(breaks = seq(0, 1250, 250), expand = c(0, 0)) +
  facet_wrap(~type, ncol = 2) +
  theme_bw(base_size = 10) +
  theme(panel.spacing = unit(1, "lines"),
        panel.background = element_blank(),
        panel.grid.major.x = element_line(color = "black"),
        panel.grid.minor.x = element_line(color = "black"),
        panel.grid.major.y = element_blank(),
        panel.grid.minor.y = element_blank(),
        panel.ontop = TRUE,
        axis.text.x = element_text(hjust = 1)) +
  scale_y_discrete(expand = c(0, 0))