如何在ggplot2中制作具有急剧过渡的色标

Question

我正在尝试创建一个色彩过渡的色标.我目前正在做的是:

test <- data.frame(x = c(1:20), y = seq(0.01, 0.2, by = 0.01))

cutoff <- 0.10

ggplot(data = test,
       aes(x = as.factor(x), y = y, fill = log(y), width = 1, binwidth = 0)) + 
 geom_bar(stat = "identity") +
 scale_fill_gradientn(colours = c("red", "red", "yellow", "green"), 
                      values = rescale(log(c(0.01, cutoff - 0.0000000000000001, cutoff, 0.2))), 
                      breaks = c(log(cutoff)), label = c(cutoff))

它正在制作我想要的情节.但是,颜色条中断的位置在某种程度上取决于截止值.有时低于价值,有时高于,有时在线.以下是一些具有不同截止值(0.05,0.06,0.1)的图:

我究竟做错了什么？或者,是否有更好的方法来创建这样的色标？

Answer 1

如果您仍然对此解决方案感兴趣，可以添加guide = guide_colourbar(nbin = <some arbitrarily large number>)到scale_fill_gradientn(). 这会增加颜色条图例使用的容器数量，从而使过渡看起来更清晰。

# illustration using nbin = 1000, & weighted colours below the cutoff
plot.cutoff <- function(cutoff){
  p <- ggplot(data = test,
              aes(x = as.factor(x), y = y, fill = log(y))) + 
    geom_col(width = 1) +
    scale_fill_gradientn(colours = c("red4", "red", "yellow", "green"), 
                         values = scales::rescale(log(c(0.01, cutoff - 0.0000000000000001, 
                                                        cutoff, 0.2))), 
                         breaks = c(log(cutoff)), 
                         label = c(cutoff),
                         guide = guide_colourbar(nbin = 1000))
  return(p)
}

cowplot::plot_grid(plot.cutoff(0.05),
                   plot.cutoff(0.06),
                   plot.cutoff(0.08),
                   plot.cutoff(0.1),
                   ncol = 2)

（如果您发现上述内容在非常高的分辨率下不够清晰，您还可以设置raster = FALSE，guide_colourbar()这会关闭插值并绘制矩形。）