我正在寻找一种在facet_wrap或facet_grid调用中动态包装条带标签文本的方法。我找到了一种使用strwrap来实现此目的的方法，但是我需要为输出指定width以根据需要工作。通常不会预先知道构面的数量，因此这种方法需要我根据数据集和绘图大小迭代调整width参数。是否可以动态指定包装函数的宽度，或者是否有其他选项可用于标记可以更好地工作的方面？
library(ggplot2)
df = expand.grid(group=paste(c("Very Very Very Long Group Name "), 1:9),
x=rnorm(5), y=rnorm(5), stringsAsFactors=FALSE)
df$groupwrap = unlist(lapply(strwrap(df$group, width=30, simplify=FALSE), paste,
collapse="\n"))
p = ggplot(df) +
geom_point(aes(x=x, y=y)) +
facet_wrap(~groupwrap)
更新：根据@baptiste和@thunk提供的指导，我想出了下面的选项。目前，它仅适用于指定的字体系列和大小，但理想情况下，应该也可以使用默认的theme设置。也许拥有ggplot2经验的人有一些改进建议。
library('grid')
grobs <- ggplotGrob(p)
sum = sum(sapply(grobs$width, function(x) convertWidth(x, "in")))
panels_width = par("din")[1] - sum # inches
df$group = as.factor(df$group)
npanels = nlevels(df$group)
if (class(p$facet)[1] == "wrap") {
cols = n2mfrow(npanels)[1]
} else {
cols = npanels
}
ps = 12
family = "sans"
pad = 0.01 # inches
panel_width = panels_width / cols
char_width = strwidth(levels(df$group)[
which.max(nchar(levels(df$group)))], units="inches", cex=ps / par("ps"),
family=family) / max(nchar(levels(df$group)))
width = floor((panel_width - pad)/ char_width) # characters
df$groupwrap = unlist(lapply(strwrap(df$group, width=width, simplify=FALSE),
paste, collapse="\n"))
ggplot(df) +
geom_point(aes(x=x, y=y)) +
facet_wrap(~groupwrap) +
theme(strip.text.x=element_text(size=ps, family=family))
答案 0 :(得分：24)
自此问题发布以来，ggplot2新功能facet_wrap(~groupwrap, labeller = labeller(groupwrap = label_wrap_gen(10)))
（＆gt; = 1.0.0，我认为）处理得很好：
facet_wrap(~groupwrap, labeller = label_wrap_gen())
请注意，您必须指定宽度才能正常工作。
对于较旧的ggplot2版本：
{{1}}
答案 1 :(得分：9)
感谢@baptiste和@thunk的指导，我创建了下面的函数，这似乎可以很好地自动包装facet标签。不过，欢迎提出改进建议。
strwrap_strip_text = function(p, pad=0.05) {
# get facet font attributes
th = theme_get()
if (length(p$theme) > 0L)
th = th + p$theme
require("grid")
grobs <- ggplotGrob(p)
# wrap strip x text
if ((class(p$facet)[1] == "grid" && !is.null(names(p$facet$cols))) ||
class(p$facet)[1] == "wrap")
{
ps = calc_element("strip.text.x", th)[["size"]]
family = calc_element("strip.text.x", th)[["family"]]
face = calc_element("strip.text.x", th)[["face"]]
if (class(p$facet)[1] == "wrap") {
nm = names(p$facet$facets)
} else {
nm = names(p$facet$cols)
}
# get number of facet columns
levs = levels(factor(p$data[[nm]]))
npanels = length(levs)
if (class(p$facet)[1] == "wrap") {
cols = n2mfrow(npanels)[1]
} else {
cols = npanels
}
# get plot width
sum = sum(sapply(grobs$width, function(x) convertWidth(x, "in")))
panels_width = par("din")[1] - sum # inches
# determine strwrap width
panel_width = panels_width / cols
mx_ind = which.max(nchar(levs))
char_width = strwidth(levs[mx_ind], units="inches", cex=ps / par("ps"),
family=family, font=gpar(fontface=face)$font) /
nchar(levs[mx_ind])
width = floor((panel_width - pad)/ char_width) # characters
# wrap facet text
p$data[[nm]] = unlist(lapply(strwrap(p$data[[nm]], width=width,
simplify=FALSE), paste, collapse="\n"))
}
if (class(p$facet)[1] == "grid" && !is.null(names(p$facet$rows))) {
ps = calc_element("strip.text.y", th)[["size"]]
family = calc_element("strip.text.y", th)[["family"]]
face = calc_element("strip.text.y", th)[["face"]]
nm = names(p$facet$rows)
# get number of facet columns
levs = levels(factor(p$data[[nm]]))
rows = length(levs)
# get plot height
sum = sum(sapply(grobs$height, function(x) convertWidth(x, "in")))
panels_height = par("din")[2] - sum # inches
# determine strwrap width
panels_height = panels_height / rows
mx_ind = which.max(nchar(levs))
char_height = strwidth(levs[mx_ind], units="inches", cex=ps / par("ps"),
family=family, font=gpar(fontface=face)$font) /
nchar(levs[mx_ind])
width = floor((panels_height - pad)/ char_height) # characters
# wrap facet text
p$data[[nm]] = unlist(lapply(strwrap(p$data[[nm]], width=width,
simplify=FALSE), paste, collapse="\n"))
}
invisible(p)
}
要使用此功能，请将其命名为print。
library(ggplot2)
df = expand.grid(group=paste(c("Very Very Very Long Group Name "), 1:4),
group1=paste(c("Very Very Very Long Group Name "), 5:8),
x=rnorm(5), y=rnorm(5), stringsAsFactors=FALSE)
p = ggplot(df) +
geom_point(aes(x=x, y=y)) +
facet_grid(group1~group)
strwrap_strip_text(p)
答案 2 :(得分：3)
（评论太长，但也不是真正的答案）
我不认为ggplot2中会直接存在一般解决方案;这是网格单元自引用的经典问题：ggplot2想要即时计算视口大小，而strwrap需要知道一个坚固的宽度来决定如何分割文本。 （有一个非常相似的问题，但我忘了何时何地）。
然而，你可以编写一个帮助函数来估计在绘图之前你需要多少包装。在伪代码中，
# takes the facetting variable and device size
estimate_wrap = function(f, size=8, fudge=1){
n = nlevels(f)
for (loop over the labels of strwidth wider than (full.size * fudge) / n){
new_factor_level[ii] = strwrap(label[ii], available width)
}
return(new_factor)
}
（需要一些标准单位转换）
当然，如果您想使用space="free"，事情会变得更复杂。
答案 3 :(得分：1)
评论时间太长，但没有完整答案。它与baptiste的回答一致，但还有一些指示：
p <- ggplot(df) + geom_point(aes(x=x, y=y)) + facet_wrap(~groupwrap)
# get the grobs of the plot and get the widths of the columns
grobs <- ggplotGrob(p)
grobs$width
# here you would have to use convertWidth from gridDebug package
# to convert all the units in the widths to the same unit (say 'pt'),
# including exctraction from the strings they are in -- also, I
# couldn't make it work neither for the unit 'null' nor for 'grobwidth',
# so you'll have to add up all the other ones, neglect grobwidth, and
# subtract all the widths that are not null (which is the width of each
# panel) from the device width
library('grid')
convertWidth(DO FOR EACH ELEMENT OF grobs$width)
sum <- SUM_UP_ALL_THE_NON-PANEL_WIDTHS
# get the width of the graphics device
device <- par('din')[1]
# get width of all panels in a row
panels_width <- device - sum
# get total number of panels in your case
df$group <- as.factor(df$group)
npanels <- nlevels(df$group)
# get number of panels per row (i.e. number of columns in graph) with
# the function that ggplot2 uses internally
cols <- n2mfrow(npanels)
# get estimate of width of single panel
panel_width <- panels_width / cols
很抱歉，这部分内容仍然不完整。但就我而言，我希望这些想法可能会有所帮助......