ggplot2：连接分组数据手段的线 [英] ggplot2: line connecting the means of grouped data

问题描述

我试图将我的数据的一个变量与另一个变量分组，然后通过手段绘制一条线。当两个变量都是数字时，它工作正常。但是，当分组变量是一个因素时，我遇到了问题。下面我有一个模拟。
$ b

  x < -  sample（1：3，40，replace = T）
y < -  rnorm（40 ）
 
 df1 < -  data.frame（x，y）
 qplot（x，y，data = df1）+ stat_summary（fun.y = mean，color =red， geom =line）
  

这看起来很棒。但是，如果x变量是一个因素，我没有得到该行。

pre $ df2 < - data.frame（x = as.factor（x），y​​）
qplot（x ，y，data = df2）+ stat_summary（fun.y = mean，color =red，geom =line）


有什么我可以做到这一行显示？

Ps。 geom =pointworks works but not geom =line

  qplot（x，y，data = df2）+ stat_summary fun.y = mean，color =red，geom =point）
  

感谢您阅读!!

解决方案

ggplot2 有意使得跨x轴系数画线是有点棘手的，因为你需要确保它有意义。如果你的X轴是纽约，费城和波士顿，绘制一条连接它们的线不是一个好主意。

然而，

然而， ，假设你的x变量有一个有意义的顺序，你必须定义 group 美学来绘制你想要的行。在这里， group = 1 。

  qplot（x，y，data = df2）+ 
 stat_summary（fun.y = mean，color =red，geom =line，aes（group = 1））
  

如果您只需将 geom_line（）添加到这样的图表中，您必须在一个图表中定义分组变量类似的方式。

I'm trying to group one variable of my data by another and then plot a line through the means. It works fine when both variables are numbers. However, I'm having a problem when the grouping variable is a factor. I have a mock up below.

x <- sample(1:3, 40, replace=T)
y <- rnorm(40)

df1 <- data.frame(x, y)
qplot(x, y, data=df1) + stat_summary(fun.y=mean, colour="red", geom="line")

This is looks great. However if the x variable is a factor I don't get the line.

df2 <- data.frame(x=as.factor(x), y)
qplot(x, y, data=df2) + stat_summary(fun.y=mean, colour="red", geom="line")

Is there something I can do to get this line displayed?

Ps. geom="point" works but not geom="line"

qplot(x, y, data=df2) + stat_summary(fun.y=mean, colour="red", geom="point")

Thanks for reading!!

解决方案

ggplot2 intentionally makes it a little tricky to draw lines across x-axis factors, because you need to make sure that it's meaningful. If your x-axis was "New York", "Philadelphia" and "Boston", it wouldn't be a good idea to draw a line connecting them.

However, assuming that your x variable has a meaningful order, you have to define the group aesthetic to draw the line you want. Here, group = 1.

qplot(x, y, data=df2) + 
  stat_summary(fun.y=mean, colour="red", geom="line", aes(group = 1))

If you just add geom_line() to a plot like this, you will have to define the grouping variable in a similar way.

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