如何在ggplot2中制作连续图例？

Question

我对 ggplot2 中的图例几乎没有疑问。如何从所附代码中连续制作图例。在此代码中，图例采用离散形式，我想将其设为连续形式（平滑连续模式）。代码是可重现的（有点长，但可能在此代码中一行会发生变化）

 library(sf)
 library(sp)

 r <- raster(t((volcano[,ncol(volcano):1] - 94) * 4.95))

 # Let's mock with a shapefile
 poly <- st_as_sfc(st_bbox(st_as_sf(rasterToPolygons(r))))

 # Sample 4 points
 set.seed(3456)

 sample <- st_sample(poly, 4)
 sample <- st_buffer(sample, c(0.01, 0.02, 0.03))
 sample <- st_sf(x=1:4, sample)
 st_write(sample, "1aa.shp", append = FALSE)
 # Mocked data

 # Now let's start with code -------

 r <- raster(t((volcano[,ncol(volcano):1] - 94) * 4.95))

 # Use sf!!
 pg <- st_read("1aa.shp") # loadshapfile 
 plot(r)
 plot(st_geometry(pg), add= TRUE,) # it appears here like first picture 
(left).

 centile90 <- quantile(r, 0.90)
 df <- as.data.frame(as(r, "SpatialPixelsDataFrame"))
 colnames(df) <- c("value", "x", "y")

 library(ggplot2)

  mybreaks <- seq(0, 500, 50)

  ggplot(df, aes(x, y, z = value)) +
  geom_contour_filled(breaks = mybreaks) +
  geom_contour(breaks = centile90, colour = "pink",
             size = 0.5) +
   # And here we have it
   geom_sf(data=pg, fill="black", inherit.aes = FALSE) +
  scale_fill_manual(values = hcl.colors(length(mybreaks)-1, "Zissou1", rev 
  = FALSE)) +
  scale_x_continuous(expand = c(0, 0)) +
  scale_y_continuous(expand = c(0, 0)) +
  theme_classic() +
  theme()

运行此代码后，我得到了这种形式的图例（附图的左侧），意味着不连续，但我想让这个图例看起来像（附图的右侧）。但在我的代码中，我给出了连续缩放的命令。有人可以告诉我如何使此代码满足所需图例的平滑连续模式。

Answer 1

您可以使用该函数geom_tile并scale_fill_gradientn获得连续比例而不是离散比例图例，如下所示：

library(ggplot2)
library(sf)
library(sp)
library(raster)
mybreaks <- seq(0, 500, 50)

ggplot(df, aes(x, y, fill = value)) +
  geom_tile() +
  scale_fill_gradientn(
    colours = hcl.colors(length(mybreaks)-1, "Zissou1", rev = FALSE), 
    breaks = mybreaks
  ) +
  geom_sf(data=pg, fill="black", inherit.aes = FALSE) +
  scale_x_continuous(expand = c(0, 0)) +
  scale_y_continuous(expand = c(0, 0)) +
  theme_classic() +
  theme()

输出：