在knitr Latex文档中缩放图形

Question

我试图将一个情节图表包含在带有knitr的Latex文档中。由于knitr包含webshot包，因此效果很好。但是，如果我想调整乳胶输出的数字，图形环境会变大，但是图表图表不会被调整到手动设置的图形宽度和高度。

指定推荐here等网页提示选项，但两者都不起作用。缩放ggplot图表效果很好，但如何才能获得相同的结果图表？

\documentclass{article}
\usepackage{cleveref}

<<setup, echo=FALSE, message = FALSE, warning = FALSE>>=
library(ggplot2)
library(plotly)
@

%Preamble
\title{GGplot vs. Plotly }
\author{authors}
\date{2016}

\begin{document}

\maketitle

\section{Comparison ggplot with plotly}

This document illustrate the difference between ggplot and plotly. The chart in (\Cref{fig:ggplot}) is well placed in the document, but the chart in (\Cref{fig:plotly}) is neither scalled to the figure width, nor positioned next to the label.

<<ggplot, fig.lp="fig:", fig.cap = 'This is rendered with ggplot()', echo=FALSE, fig.width = 10, fig.height = 6>>=
ggplot(midwest, aes(x = state, y = percollege, colour = state)) + geom_boxplot()
@

<<plotly, fig.lp="fig:", fig.cap = 'This is rendered with plotly()', echo=FALSE, fig.width = 10, fig.height = 6, screenshot.opts = list(delay = 2, cliprect = 'viewport')>>=
plot_ly(midwest, x = ~state, y = ~percollege, color = ~state, type = "box")
@

\end{document}

我看到图形文件 figure / plotly-1.pdf （由knitr / webshot生成，然后加载到latex中）有两页，而plotly对象位于左上角的某处。我想webshot数字中包含的边距实际上是问题所在。

R 3.2.3 knitr 1.14 ggplot2 2.1.0 情节4.5.2