试试这个ggplot2的方法： （-10，10,0.1）
df df $ t dfm
ggplot（NULL，aes（x，value））+
geom_line（aes（color = variable），
小滴（子集（dfm，变量％in％c（y1，y2 ）））+
geom_rect（aes（xmin = x - 0.05，xmax = x + 0.05，ymin = -0.5，ymax = -0.4，fill = value），
子集（dfm，variable ==t））

更新

您可以使用 scale_fill_XXX 。这里是一个喷墨颜色版本：

  jet.colors<  -  colorRampPalette（c（＃00007F，blue ，＃007FFF，青色，＃7FFF7F，黄色，＃FF7F00，红色，＃7F0000））

＃ $ bp  geom_line（aes（color = variable），
小滴（子集（dfm，变量％in％c（y1， y2）））+ 
 geom_rect（aes（xmin = x-0.05，xmax = x + 0.05，ymin = -0.5，ymax = -0.4，fill = value），
子集（dfm ，变量==t））+ 
 scale_fill_gradientn（colors = jet.colors（7））
p 
 

，而在ggplot2的下一个版本中，您可以使用colorbar作为图例。

 ＃面板在右侧
p + guides（fill =colourbar）
 

I have a tricky question regarding to what i'm trying to do. I have a plot with two lines (the mean of two conditions) on it. I want to add on the same plot a square reflecting the t-values (and colored according to these values in a gradient way). How could i add this square?

Well since i don't know if i'm clear, here is a figure of what i try to achieve.

Thank you for any help!

Try this for ggplot2 way:

x <- seq(-10, 10, 0.1)
df <- data.frame(x, y1 = pnorm(x), y2 = pnorm(x) * 2)
df$t <- df$y2 - df$y1
dfm <- melt(df, id = "x")

ggplot(NULL, aes(x, value)) + 
  geom_line(aes(colour = variable), 
            droplevels(subset(dfm, variable %in% c("y1", "y2")))) +
  geom_rect(aes(xmin = x - 0.05, xmax = x + 0.05, ymin = -0.5, ymax = -0.4, fill = value),
            subset(dfm, variable == "t"))

UPDATED

You can use scale_fill_XXX. Here is a jet-color version:

jet.colors <- colorRampPalette(c("#00007F", "blue", "#007FFF", "cyan","#7FFF7F", "yellow", "#FF7F00", "red", "#7F0000"))

# panel on the left side
p <- ggplot(NULL, aes(x, value)) + 
  geom_line(aes(colour = variable), 
            droplevels(subset(dfm, variable %in% c("y1", "y2")))) +
  geom_rect(aes(xmin = x - 0.05, xmax = x + 0.05, ymin = -0.5, ymax = -0.4, fill = value),
            subset(dfm, variable == "t")) + 
  scale_fill_gradientn(colours = jet.colors(7))
p

and in the next version of ggplot2, you can use colorbar as the legend.

  # panel on the right side
  p + guides(fill = "colourbar")