R：ggplot2：facet_grid：如何在少数（不是全部）标签中包含数学表达式？ [英] R : ggplot2 : facet_grid : how include math expressions in few (not all) labels?

问题描述

我在 ggplot2 中遇到了一些问题。我读了大部分相关文章，尝试了一些东西，但没有找到任何真正的解决方案。

我想在我的标签中包含数学表达式， facet_grids 与 ggplot2 。

• ，我不能写出名称μg.L-1


• 在title和axis中，我可以这样做，例如：
  qplot（day，activity ，数据= a）+ xlab（表达式（100μg* .L ^ - 1*））：这是行之有效的



• 我如何处理facet_labels？
  我可以设置关卡并重命名标签因子，但不考虑表达式，例如：
  
  

  levels（a $ group）<-c（control，expression（100μg* .L ^ - 1*））

  
  
  
  
  
  qplot（...，facets =〜group）
p>结果：






标签facet 1写在图表上：control

<图片上写有方面2的标签：100μg .L ^ - 1...





$



我不想使用 facet_grid（。〜group，labeller = label_bquote（...）），因为我不希望所有标签都遵循相同的表达式。我想一个一个编辑标签手动 ...
我尝试使用 bquote（...）而不是表达式（...）但同样不好的结果会发生





有人对此有任何线索吗？



---





一个例子：我定义一个数据框：



  activity< - 如数字（44，41，48，43，42，45，44，39，47，68，88 ，57））
 group <-c（first，first，first，first，first，first，
second，second ，秒，秒，秒，秒）
日<-c（0，0，0，20，20，20 0，0，0，20，20，20）
 a <-data.frame（activity，group，day）
  

I plot：



  require（ggplot2 ）
  

qplot（day，activity，facets =。〜group，data = a，ylim = c（25,90））








我想更改facet标签的名称和y轴：
$ b $ pre $ levels（a $ group）<-c（control，expression（100μg* .L ^ -1*））
qplot（day，activity，facets =。〜group，data = a，ylim = c（25,90），
ylab = expression（fmol* .μl^ - 1*））






解释





我们创建标签结构作为字符串，我们创建一个公式，注意使用〜来替换空格...然后我们告诉 facet_grid（） labeller = label_parsed ...



来解析传递给它的标签字符串。注意：显示细节在？plotmath 中进行了描述，但请注意 geom_text（）和 facet_grid（）使用字符串，而不是表达式。




我希望以上内容能够帮助您。





参考：





请参阅Hagley Wickham关于贴标签的页面： https://github.com/hadl ey / ggplot2 / wiki / labeller




I get stuck with something on ggplot2. I read most of the related posts, tried things but did not find any real solution.

I want to include mathematical expressions in the label of my facet_grids with ggplot2.

• In the raw file, I cannot write the name µg.L-1
• In the titles and axis I can do it, for example : qplot(day, activity, data=a) +xlab(expression("100 µg "*.L^"-1"*"")) : this is working well.

• How do I do for the facet_labels ? I can set the levels and rename the labels factors but the expression is not taken into account, for example :

  levels(a$group) <- c("control", expression("100 µg "*.L^"-1"*""))

  qplot(…, facets=~group)

Results :

Label of facet 1 is written on the graph : control

Label of facet 2 is written on the graph : "100 µg ".L^"-1""" …

and I don’t want that.

I don’t want to use facet_grid(.~group, labeller=label_bquote(…)) because I don’t want all my labels to follow the same expression. I want to edit the labels one by one manually… I tried with bquote(…) instead of expression(…) but the same bad result happens

Does someone have any clue with this?

---

An example: I define a dataframe :

activity<- as.numeric(c("44","41","48","43","42","45","44","39", "47", "68", "88", "57"))
group<-c("first","first","first","first","first","first",
         "second","second","second","second","second","second")
day<- c("0", "0", "0", "20","20", "20","0", "0", "0", "20","20", "20" )
a<-data.frame(activity, group, day)

I plot :

require (ggplot2) 

qplot(day, activity, facets=.~group, data=a, ylim=c(25,90))

I want to change the name of the facet labels and the y axis :

levels(a$group)<- c("control", expression("100 µg "*.L^"-1"*""))
qplot(day, activity, facets=.~group, data=a, ylim=c(25,90),
  ylab=expression("fmol "*.µl^"-1"*""))

It works well with the y-axis, however for the facet label, it does not work... Any clue ?

解决方案

Proposed Solution:

Prequisite:

activity <- as.numeric(c("44", "41", "48", "43", "42", "45", 
  "44", "39", "47", "68", "88", "57"))
group <- c("first", "first", "first", "first", "first", "first", 
  "second", "second", "second", "second", "second", "second")
day <- c("0", "0", "0", "20", "20", "20", "0", "0", "0", "20", 
  "20", "20")
a <- data.frame(activity, group, day)
require(ggplot2)
levels(a$group) <- c("control", expression("100 µg " * .L^"-1" * ""))

Proposed Solution:

p1 <- qplot(day, activity, data = a)
p1 + facet_grid(. ~ group, labeller = label_parsed)

result:

Explanation

We create the labels structure as a string, where we create a formula, noting to use ~ to replace spaces... We then tell facet_grid() to parse the label string passed to it as a formula by setting labeller = label_parsed...

Note: The details of the display are described in ?plotmath, but note that geom_text() and facet_grid() use strings, not expressions.

I hope the above helps.

Reference:

See Hagley Wickham's page on labellers...: https://github.com/hadley/ggplot2/wiki/labeller

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