附加geom_point与ggplot组=变量 [英] additional geom_point with ggplot group = variable

问题描述

是否可以包含group = variable并在ggplot中添加另一个点。

Is it possible to include group = variable and add another point in ggplot.

例如：

For example:

require(MuMIn)
require(ggplot2)

data(Cement)
d <- data.frame(Cement)
dd <- melt(d,id.var = "y")
d2 <- runif(length(dd[,1]))
d2 <- data.frame(first = dd$y,
                 second = d2)

ggplot(dd, aes(x = y,y = value,group = variable)) + 
  geom_line() + 
  geom_point(data = d2,aes(x = first,y = second))

这会导致错误。最终我想将这里指定的点添加到线条图上。

This leads to an error. Eventually I would like to add the points specified here onto the line plot.

推荐答案

中的映射美学遵循一种继承模式。当您将美学设计为顶级时，在 ggplot（）中，它们会自动传递到所有后续图层。

Mapped aesthetics in ggplot2 follow a sort of inheritance pattern. When you map aesthetics at the "top" level, in ggplot(), they are automatically passed down to all subsequent layers.

这意味着 geom_point 正在寻找 d2 中的变量 code>。它不会查找 y 或值列，因为您明确地将x和y美学重新映射到 geom_point（）。

This means that geom_point is looking for a variable column in d2. It won't look for y or value columns, since you explicitly re-mapped the x and y aesthetics in geom_point().

解决方案是将顶级审美映射从 ggplot （）到 geom_line（），或者 un-map group geom_point 使用 group = NULL 。

The solution is either to move the top level aesthetic mappings from ggplot() to geom_line(), or to un-map group in geom_point using group = NULL.

另外，Didzis在评论中指出了第三种解决方案，即将 inherit.aes = FALSE 添加到 geom_point 。

Additionally, Didzis pointed out a third solution in the comments, which is to add inherit.aes = FALSE to geom_point.

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