将 ggplot geom_polygon 扩展到绘图结束

Question

How can I make a confidence interval band that extends to the end of the plot in ggplot?

I can do it if the plotted band is entirely within the plot, for example

limits <- c(1e2, 1e7)
confPolygon <- tibble(
    x = c(limits[1], limits[1]*10, limits[2], limits[2], limits[2]/10, limits[1], limits[1]), 
    y = c(limits[1], limits[1], limits[2]/10, limits[2], limits[2], limits[1]*10, limits[1])
)
plot <- ggplot() + 
    geom_polygon(data = confPolygon, aes(x = x, y = y), fill = "grey", alpha = .25) +
    scale_x_log10(limits = limits) + 
    scale_y_log10(limits = limits)

works. However, if I try any shape that extends the polygon to the edges

confPolygon <- tibble(
    x = c(limits[1], limits[2]*10, limits[2]*10, limits[1], limits[1]), 
    y = c(limits[1], limits[1], limits[2]*10, limits[2]*10, limits[1])
)

then it doesn't plot the polygon.

Answer 1

The reason is because the method you are using to zoom in to the plot (setting limits within the x or y scales) isn't meant to zoom in; it actually subsets the data, accidentally creating missing values on the way. Use coord_cartesian(xlim = c(0,5), ylim = c(0,5)) , or in your case, coord_cartesian(xlim = limits, ylim = limits) instead, as this step does not subset the data.

Answer 2

One way to do this is with oob=scales::squish() .

plot2 <- ggplot() + 
  geom_polygon(data = confPolygon, aes(x = x, y = y), fill = "grey", alpha = .25) +
  scale_x_log10(limits = limits, oob=scales::squish) + 
  scale_y_log10(limits = limits, oob=scales::squish)

If you really want the polygon to extend all the way to the edge, you should also add expand=c(0,0) to each of the scale_*_log10() argument lists.