如何在 R 中制作渐变颜色填充时间序列图

问题描述

如何用渐变色填充(sp)线下方和上方的区域?

这个例子是在 Inkscape 中绘制的 - 但我需要 垂直渐变 - 不是水平的.

This example has been drawn in Inkscape - BUT I NEED vertical gradient - NOT horizontal.

从零到正的间隔==从白色到红色.

从零到负的间隔==从白色到红色.

是否有任何包可以做到这一点?

Is there any package which could do this?

我捏造了一些源数据....

I fabricated some source data....

set.seed(1)
x<-seq(from = -10, to = 10, by = 0.25)
data <- data.frame(value = sample(x, 25, replace = TRUE), time = 1:25)
plot(data$time, data$value, type = "n")
my.spline <- smooth.spline(data$time, data$value, df = 15)
lines(my.spline$x, my.spline$y, lwd = 2.5, col = "blue")
abline(h = 0)

推荐答案

这是 base R 中的一种方法，我们用渐变颜色的矩形填充整个绘图区域，然后填充反色用白色标记感兴趣的区域.

And here's an approach in base R, where we fill the entire plot area with rectangles of graduated colour, and subsequently fill the inverse of the area of interest with white.

shade <- function(x, y, col, n=500, xlab='x', ylab='y', ...) {
  # x, y: the x and y coordinates
  # col: a vector of colours (hex, numeric, character), or a colorRampPalette
  # n: the vertical resolution of the gradient
  # ...: further args to plot()
  plot(x, y, type='n', las=1, xlab=xlab, ylab=ylab, ...)
  e <- par('usr')
  height <- diff(e[3:4])/(n-1)
  y_up <- seq(0, e[4], height)
  y_down <- seq(0, e[3], -height)
  ncolor <- max(length(y_up), length(y_down))
  pal <- if(!is.function(col)) colorRampPalette(col)(ncolor) else col(ncolor)
  # plot rectangles to simulate colour gradient
  sapply(seq_len(n),
         function(i) {
           rect(min(x), y_up[i], max(x), y_up[i] + height, col=pal[i], border=NA)
           rect(min(x), y_down[i], max(x), y_down[i] - height, col=pal[i], border=NA)
         })
  # plot white polygons representing the inverse of the area of interest
  polygon(c(min(x), x, max(x), rev(x)),
          c(e[4], ifelse(y > 0, y, 0),
            rep(e[4], length(y) + 1)), col='white', border=NA)
  polygon(c(min(x), x, max(x), rev(x)),
          c(e[3], ifelse(y < 0, y, 0),
            rep(e[3], length(y) + 1)), col='white', border=NA)
  lines(x, y)
  abline(h=0)
  box()
}

以下是一些示例:

xy <- curve(sin, -10, 10, n = 1000)
shade(xy$x, xy$y, c('white', 'blue'), 1000)

或者使用由色带调色板指定的颜色:

Or with colour specified by a colour ramp palette:

shade(xy$x, xy$y, heat.colors, 1000)

并应用于您的数据，尽管我们首先将这些点插值到更精细的分辨率(如果我们不这样做，梯度不会紧密地沿着与零交叉的线).

And applied to your data, though we first interpolate the points to a finer resolution (if we don't do this, the gradient doesn't closely follow the line where it crosses zero).

xy <- approx(my.spline$x, my.spline$y, n=1000)
shade(xy$x, xy$y, c('white', 'red'), 1000)

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