ggplot2中的离散图例中断 [英] Discrete legend breaks in ggplot2

问题描述

我想将图例分为几类，而不要使用连续的颜色范围.有人可以帮我解决我在这里使用的特定示例吗?以下是我目前在40、60和80时的色彩中断测试.非常感谢！

I'd like to break the legend into categories rather than having a continuous range of colours. Could someone kindly help me for the specific example I am using here? Below is my current trial with colour breaks at 40, 60 and 80. Thank you very much!

library(raster)
library(ggplot2)
library(maptools)
data("wrld_simpl")

#sample raster
r <- raster(ncol=10, nrow=20)
r[] <- 1:ncell(r)
extent(r) <- extent(c(-180, 180, -70, 70))

#plotting
var_df <- as.data.frame(rasterToPoints(r))
p <- ggplot() +
  geom_polygon(data = wrld_simpl[wrld_simpl@data$UN!="10",], 
               aes(x = long, y = lat, group = group),
               colour = "black", fill = "grey")
p <- p + geom_raster(data = var_df, aes(x = x, y = y, fill = layer))
p <- p + coord_equal() +  theme_bw()  +labs(x="", y="") 
p <- p + theme(legend.key=element_blank(), 
               axis.text.y =element_text(size=16),
               axis.text.x =element_text(size=16),
               legend.text =element_text(size=12), 
               legend.title=element_text(size=12))
# p <- p + scale_fill_gradientn(colours = rev(terrain.colors(10)))
p <- p + scale_colour_manual(values = c("red", "blue", "green","yellow"), 
                             breaks = c("40", "60", "80", max(var_df$layer)),
                             labels = c("1-40", "40-60", "60-80", "80+"))
p <- p + geom_polygon(data = wrld_simpl[wrld_simpl@data$UN!="10",], 
                      aes(x = long, y = lat, group = group), 
                      colour = "black", fill = NA) 
p

当前连续图例:

带有中断的图例示例

推荐答案

在这里.我从此处

library(raster)
library(ggplot2)
library(maptools)

# Plot discrete colorbar function
plot_discrete_cbar = function (
  # Vector of breaks. If +-Inf are used, triangles will be added to the sides of the color bar      
  breaks, 
  palette = "Greys", # RColorBrewer palette to use
  # Alternatively, manually set colors
  colors = RColorBrewer::brewer.pal(length(breaks) - 1, palette), 
  direction = 1, # Flip colors? Can be 1 or -1
  spacing = "natural", # Spacing between labels. Can be "natural" or "constant"
  border_color = NA, # NA = no border color
  legend_title = NULL,
  legend_direction = "horizontal", # Can be "horizontal" or "vertical"
  font_size = NULL,
  expand_size = 1, # Controls spacing around legend plot
  spacing_scaling = 1, # Multiplicative factor for label and legend title spacing
  width = 0.1, # Thickness of color bar
  triangle_size = 0.1 # Relative width of +-Inf triangles
  ) {

  require(ggplot2)

  if (!(spacing %in% c("natural", "constant"))) stop("Spacing must be either 'natural' or 'constant'")
  if (!(direction %in% c(1, -1))) stop("Direction must be either 1 or -1")
  if (!(legend_direction %in% c("horizontal", "vertical"))) { 
    stop("Legend_direction must be either 'horizontal' or 'vertical'")
  }

  breaks = as.numeric(breaks)
  new_breaks = sort(unique(breaks))
  if (any(new_breaks != breaks)) warning("Wrong order or duplicated breaks")
  breaks = new_breaks
  if (class(colors) == "function") colors = colors(length(breaks) - 1)
  if (length(colors) != length(breaks) - 1) {
    stop("Number of colors (", length(colors), ") must be equal to number of breaks (", 
         length(breaks), ") minus 1")
  }
  if (!missing(colors)) {
    warning("Ignoring RColorBrewer palette '", palette, "', since colors were passed manually")
  }
  if (direction == -1) colors = rev(colors)

  inf_breaks = which(is.infinite(breaks))
  if (length(inf_breaks) != 0) breaks = breaks[-inf_breaks]
  plotcolors = colors

  n_breaks = length(breaks)

  labels = breaks

  if (spacing == "constant") {
    breaks = 1:n_breaks
  }

  r_breaks = range(breaks)

  if(is.null(font_size)) {
    print("Legend key font_size not set. Use default value = 5")
    font_size <- 5
  } else {
    print(paste0("font_size = ", font_size))
    font_size <- font_size
  }

  cbar_df = data.frame(stringsAsFactors = FALSE,
                       y = breaks,
                       yend = c(breaks[-1], NA),
                       color = as.character(1:n_breaks)
  )[-n_breaks,]

  xmin = 1 - width/2
  xmax = 1 + width/2

  cbar_plot = ggplot(cbar_df, aes(xmin = xmin, xmax = xmax, 
                                  ymin = y, ymax = yend, fill = color)) +
    geom_rect(show.legend = FALSE,
              color = border_color)

  if (any(inf_breaks == 1)) { # Add < arrow for -Inf
    firstv = breaks[1]
    polystart = data.frame(
      x = c(xmin, xmax, 1),
      y = c(rep(firstv, 2), firstv - diff(r_breaks) * triangle_size)
    )
    plotcolors = plotcolors[-1]
    cbar_plot = cbar_plot +
      geom_polygon(data = polystart, aes(x = x, y = y),
                   show.legend = FALSE,
                   inherit.aes = FALSE,
                   fill = colors[1],
                   color = border_color)
  }

  if (any(inf_breaks > 1)) { # Add > arrow for +Inf
    lastv = breaks[n_breaks]
    polyend = data.frame(
      x = c(xmin, xmax, 1),
      y = c(rep(lastv, 2), lastv + diff(r_breaks) * triangle_size)
    )
    plotcolors = plotcolors[-length(plotcolors)]
    cbar_plot = cbar_plot +
      geom_polygon(data = polyend, aes(x = x, y = y),
                   show.legend = FALSE,
                   inherit.aes = FALSE,
                   fill = colors[length(colors)],
                   color = border_color)
  }

  if (legend_direction == "horizontal") { # horizontal legend
    mul = 1
    x = xmin
    xend = xmax
    cbar_plot = cbar_plot + coord_flip()
    angle = 0
    legend_position = xmax + 0.1 * spacing_scaling
  } else { # vertical legend
    mul = -1
    x = xmax
    xend = xmin
    angle = -90
    legend_position = xmax + 0.2 * spacing_scaling
  }

  cbar_plot = cbar_plot +
    geom_segment(data = data.frame(y = breaks, yend = breaks),
                 aes(y = y, yend = yend),
                 x = x - 0.05 * mul * spacing_scaling, xend = xend,
                 inherit.aes = FALSE) +
    annotate(geom = 'text', x = x - 0.1 * mul * spacing_scaling, y = breaks,
             label = labels,
             size = font_size) +
    scale_x_continuous(expand = c(expand_size, expand_size)) +
    scale_fill_manual(values = plotcolors) +
    theme_void()

  if (!is.null(legend_title)) { # Add legend title
    cbar_plot = cbar_plot +
      annotate(geom = 'text', x = legend_position, y = mean(r_breaks),
               label = legend_title,
               angle = angle,
               size = font_size)
  }

  return(cbar_plot)
}

将数据切割到离散色条的箱中

Cut data into bins for the discrete colorbar

myvalues <- c(seq(0, 200, 40), Inf) 
var_df$cuts <- cut(var_df$layer, myvalues, include.lowest = TRUE) 
levels(var_df$cuts)
#> [1] "[0,40]"    "(40,80]"   "(80,120]"  "(120,160]" "(160,200]" "(200,Inf]"

绘制栅格

p <- ggplot() +
  geom_polygon(data = wrld_simpl[wrld_simpl@data$UN != "10", ], 
               aes(x = long, y = lat, group = group),
               colour = "black", fill = "grey")
p <- p + geom_raster(data = var_df, aes(x = x, y = y, fill = cuts)) # matching cuts & fill
p <- p + coord_equal() + theme_minimal() + labs(x="", y="") 
p <- p + theme(legend.key  =element_blank(), 
               axis.text.y =element_text(size=16),
               axis.text.x =element_text(size=16),
               legend.text =element_text(size=12), 
               legend.title=element_text(size=12))
p <- p + scale_fill_brewer("Layer", palette = "YlGnBu", drop = FALSE)
p <- p + geom_polygon(data = wrld_simpl[wrld_simpl@data$UN != "10", ], 
                      aes(x = long, y = lat, group = group), 
                      colour = "black", fill = NA) 
p <- p + theme(legend.position = "none")

绘制离散色条

dbar <- plot_discrete_cbar(myvalues,
                         palette = "YlGnBu", 
                         legend_title = NULL,
                         spacing = "natural")

# reduce top and bottom margins
p1 <- p + theme(plot.margin = unit(c(10, 10, -35, 10), "pt"))
dbar <- dbar + theme(plot.margin = unit(c(-35, 10, -30, 10), "pt"))

将两个地块组合在一起

# devtools::install_github('baptiste/egg')
library(egg)
ggarrange(p1, dbar, nrow = 2, ncol = 1, heights = c(1, 0.4))

^{由 reprex软件包(v0.2.1.9000)创建于2018-10-18}

^{Created on 2018-10-18 by the reprex package (v0.2.1.9000)}

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