控制ggplot2 facet height独立于行facet的数量

Question

问题

ggplot2/knitr强制绘图(在LaTeX中)具有默认的宽高比.具有不同面数的两个图导致具有小平面高度的图.这不好.

我正在寻找一种独立于行方面数量来控制ggplot2方面高度的解决方案.

编辑9月9日: 解决方案应该在一个块内工作,因为两个块都在一个块中(如示例代码中所示).因此,调整knitr的数字相关块选项是不可行的,因为块选项同样适用于两个图.

解决方案 - 但有问题

将每个绘图放入gridExtra框并使用facet的数量缩放它的高度,导致不再有不同的facet高度:更好但不完美.

• 页面上出现的图表边距太大,即使下面还有剩余文本,因此图表的移动距离会更近.
• 看起来由此操纵的情节得到裁剪.

是否有一个更智能,无问题的解决方案,可以独立于行方面的数量控制ggplot2方面的高度？

\documentclass[a4paper]{article}
\usepackage[margin=1in]{geometry}

\begin{document}

<<setup, results='asis', message=FALSE, echo=FALSE>>=
require(ggplot2)
require(gridExtra)

### Generate two data frames

# Data frame with 2 classes
db.small = data.frame (
  class = as.factor(c(rep("A", 12), rep("B", 12))),
  month = as.factor(rep(1:12, 2)),
  value = runif(2*12, 0, 100)
  )

# Data frame with 5 classes
db.large = data.frame (
  class = as.factor(c(rep("A", 12), rep("B", 12), rep("C", 12), rep("C", 12), rep("D", 12))),
  month = as.factor(rep(1:12, 5)),
  value = runif(5*12, 0, 100)
)

# Generate plots
plot1 = ggplot(db.small, aes(month, value)) + geom_bar(stat="identity") + facet_grid(class ~ .) + ylim(c(0, 100))
plot2 = ggplot(db.large, aes(month, value)) + geom_bar(stat="identity") + facet_grid(class ~ .) + ylim(c(0, 100))
@

\section{Before: Native plots without modification}
Ggplot2/knitr forces both plots to have the default aspect ratio. As both plots have different number of facets the result is that the facet heights are different. This is not nice.

<<before, results='asis', message=FALSE, echo=FALSE, out.width="0.6\\linewidth">>=
print(plot1)
print(plot2)
@

\pagebreak
\section{After: Plots with modification}
Putting each plot into a gridExtra box and scaling it's height with the number of facets, results in facet heights which are no longer different: nicer but not perfect, see problems below.

<<After, results='asis', message=FALSE, echo=FALSE, out.width="0.6\\linewidth">>=
# Calculate number of facets for the two plots
db.small.numberfacets = length(unique(db.small$class))
db.large.numberfacets = length(unique(db.large$class))

# Define heights for modification of plots
facet.height = 4
other.height = 2

plot1 = plot1 + theme( plot.margin = unit(c(0, 0, 0, 0), "cm"))
plot2 = plot2 + theme( plot.margin = unit(c(0, 0, 0, 0), "cm"))

# Put plots inside a gridExtra box and change height plots
grid.arrange(arrangeGrob(plot1, heights=unit(db.small.numberfacets*facet.height+other.height, "cm")), nrow=1)
grid.arrange(arrangeGrob(plot2, heights=unit(db.large.numberfacets*facet.height+other.height, "cm")), nrow=1)
@


2 Problems:
\begin{itemize}
\item Plots appear on the page with too much margin, even there's remaining text below so plots shall move more closer.
\item Seems the second plot is cropped, see the x-axis label.
\end{itemize}

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\end{document}

pdf输出:

Answer 1

您知道 knitr块选项可以采用任意 R 表达式吗？示例40显示了如何动态计算fig.width和fig.height。

fig.height对于您的情况，您可以根据因子变量中用于分面的级别数分配一个值。例如，

\documentclass{article}

\begin{document}
<<setup>>=
library(ggplot2)
calc_height = function(f) length(levels(f))
p = ggplot(diamonds, aes(color)) + geom_bar()
@

<<test-a, fig.width=7, fig.height=calc_height(diamonds$cut)>>==
p + facet_grid(cut ~ .)
@

<<test-b, fig.width=7, fig.height=calc_height(diamonds$clarity)>>==
p + facet_grid(clarity ~ .)
@

\end{document}

输出：