左对齐多行构面标签中的文本 [英] Left justify text from multi-line facet labels

问题描述

我正在使用facet_grid()来显示一些数据，并且我的facet标签跨越了多行文本(它们包含"\ n"字符).

I'm using facet_grid() to display some data, and I have facet labels that span multiple lines of text (they contain the "\n" character).

require(ggplot2)

#Generate example data
set.seed(3)
df = data.frame(facet_label_text = rep(c("Label A",
                                         "Label B\nvery long label",
                                         "Label C\nshort",
                                         "Label D"),
                                       each = 5),
                time = rep(c(0, 4, 8, 12, 16), times = 4),
                value = runif(20, min=0, max=100))

#Plot test data
ggplot(df, aes(x = time, y = value)) +
    geom_line() +
    facet_grid(facet_label_text ~ .) +
    theme(strip.text.y = element_text(angle = 0, hjust = 0))

因此，通过使用hjust = 0参数，我可以将构面标签文本左对齐为一个单元.

So by using the hjust = 0 argument, I can left-align facet label text as a unit.

我想做的是将每一行文本左对齐.因此，标签B"和很长标签"它们都沿左侧对齐，而不是相对于彼此居中(标签C"和短"的同上). ggplot2有可能吗?

What I would like to do is left-align each individual line of text. So "Label B" and "very long label" are both aligned along the left side, rather than centered relative to each other (ditto for "Label C" and "short"). Is this possible in ggplot2?

推荐答案

使用网格的grid.gedit函数编辑条带非常简单.

This is fairly straightforward using grid's grid.gedit function to edit the strips.

library(ggplot2)  # v2.1.0
library(grid)

# Your data
set.seed(3)
df = data.frame(facet_label_text = rep(c("Label A",
                                         "Label B\nvery long label",
                                         "Label C\nshort",
                                         "Label D"), 
                                       each = 5),
                time = rep(c(0, 4, 8, 12, 16), times = 4),
                value = runif(20, min=0, max=100))

# Your plot
p = ggplot(df, aes(x = time, y = value)) +
    geom_line() +
    facet_grid(facet_label_text ~ .) +
    theme(strip.text.y = element_text(angle = 0, hjust = 0))
p

# Get a list of grobs in the plot
grid.ls(grid.force())  

# It looks like we need the GRID.text grobs.
# But some care is needed:
# There are GRID.text grobs that are children of the strips;
# but also there are GRID.text grobs that are children of the axes.
# Therefore, a gPath should be set up 
# to get to the GRID.text grobs in the strips

# The edit
grid.gedit(gPath("GRID.stripGrob", "GRID.text"),  
         just = "left", x = unit(0, "npc"))

或者，还有几行代码可用于grob对象(代替上面的屏幕编辑):

Or, a few more lines of code to work with a grob object (in place of editing on screen as above):

# Get the ggplot grob
gp = ggplotGrob(p)
grid.ls(grid.force(gp))

# Edit the grob
gp = editGrob(grid.force(gp), gPath("GRID.stripGrob", "GRID.text"), grep = TRUE, global = TRUE,
          just = "left", x = unit(0, "npc"))

# Draw it
grid.newpage()
grid.draw(gp)

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