将图例中的图例标题和图例中心对齐ggplot2中较长的图例标题 [英] Center-align legend title and legend keys in ggplot2 for long legend titles

问题描述

当图例标题很长时，我很难将图例的标题与图例中心对齐。有一个问题来自

一切都如预期，图例标题集中在图例关键字上方。

现在相同的长传说标题：

  ggplot（虹膜，aes（x = Sepal.Len gth，y = Sepal.Width，color = Petal.Width））+ geom_point（size = 3）+ 
 scale_color_distiller（palette =YlGn，type =seq，direction = -1，
 name =Long legend heading\\\
Should be centered）+ 
 theme（legend.title.align = 0.5）
  

我们可以看到文本与中心对齐，但不是相对于传奇钥匙。我曾尝试修改其他主题选项，例如 legend.justification =center，但似乎没有将该按键从图例框中最左侧的位置移开。 / p>

一些评论：

• 我正在运行开发版本ggplot2，v2.2.1.9000从几天前。

我特别需要一个连续调色板的解决方案。

解决方案

您必须更改源代码。目前它计算标题grob和酒吧的宽度+标签和左对齐酒吧+标签在视口（gtable）中。这是硬编码。

I am having a hard time making the title of a legend center-aligned relative to the legend keys when the legend title is long. There is a question from a year ago that works for short titles, but it doesn't seem to work for long ones.

Example, first with a short legend title:

library(ggplot2)
ggplot(iris, aes(x=Sepal.Length, y=Sepal.Width, color=Petal.Width)) + geom_point(size = 3) +
  scale_color_distiller(palette = "YlGn", type = "seq", direction = -1,
                        name = "A") +
  theme(legend.title.align = 0.5)

Everything is as expected, the legend title is centered above the legend key.

Now the same with a long legend title:

ggplot(iris, aes(x=Sepal.Length, y=Sepal.Width, color=Petal.Width)) + geom_point(size = 3) +
  scale_color_distiller(palette = "YlGn", type = "seq", direction = -1,
                        name = "Long legend heading\nShould be centered") +
  theme(legend.title.align = 0.5)

We can see that the text is center aligned to itself but not relative to the legend key. I have tried modifying other theme options, such as legend.justification = "center", but none seem to move the key from its left-most position in the legend box.

A couple of comments:

• I'm running the development version of ggplot2, v2.2.1.9000 from a few days ago.

• I specifically need a solution for a continuous colorscale palette.

解决方案

you'd have to change the source code. Currently it computes the widths for the title grob and the bar+labels, and left-justifies the bar+labels in the viewport (gtable). This is hard-coded.

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