如何使用 Sweave 控制回波宽度

Question

我对 sweave 中 echo 的输出宽度有疑问，我有一个包含大量文本的列表。问题是来自 R 的回显响应超出了 pdf 页面的范围。我尝试过使用

<<>>=
options(width=40)
@

但这并没有改变任何东西。

一个例子：设置列表（不显示在乳胶中）。

<<echo=FALSE>>=
my_list <- list(example="Site location was fixed using a Silvia Navigator handheld GPS     in October 2003.  Point of reference used was the station Bench Mark. If the bench mark location was remote from the site then the point of reference used was changed to the 0-1 metre gauge. Bench Mark location was then recorded as a separate entry in the Site History section [but not used as the site location].\r\nFor a Station location map and all digital photograph's of the station, river reach, and site details see H:\\hyd\\dat\\doc.  For non digital photo's taken prior to October 2003 please see the relevant station file at Tumut office.")
@

并显示列表的条目。

<<>>=
my_list
@

有什么方法可以让它工作而不必用 cat 语句分解列表。

Answer 1

您可以使用 capture.output() 捕获列表的打印表示，然后使用 writeLines() 和 strwrap() 来显示此内容输出，包装精美。由于 capture.output() 返回一个包含对象打印表示的字符串向量，我们可以将它们中的每一个捕获到屏幕/页面，但使用 strwrap() 进行包装。这种方法的好处是结果看起来就像是由 R 打印的。解决方案如下：

writeLines(strwrap(capture.output(my_list)))

它会产生：

$example
[1] "Site location was fixed using a Silvia Navigator
handheld GPS in October 2003.  Point of reference used
was the station Bench Mark. If the bench mark location
was remote from the site then the point of reference used
was changed to the 0-1 metre gauge. Bench Mark location
was then recorded as a separate entry in the Site History
section [but not used as the site location].\r\nFor a
Station location map and all digital photograph's of the
station, river reach, and site details see
H:\\hyd\\dat\\doc.  For non digital photo's taken prior
to October 2003 please see the relevant station file at
Tumut office."

Answer 2

来自 Mark Schwartz 2010 年发布到 rhelp 的文章：

cat(paste(strwrap(x, width = 70), collapse = "\\\\\n"), "\n")