# Press Enter in LyX Sweave as You Wish

### Yihui Xie / 2010-02-18

Note: this post is seriously out-of-date, and you should ignore it completely. See the Sweave manual for instructions with latest versions of LyX.

You have been warned above.

For a long time I’ve been wondering why we are not able to use Enter in the LyX Scrap environment which was set up by Gregor Gorjanc for Sweave. Two weeks ago, I (finally!) could not help asking Gregor about this issue, as I’m using LyX + Sweave” more and more in my daily work. He explained it here: LyX-Sweave: mandatory use of control+enter in code chunks

After digging into the LyX customization manual for a while, I found a solution which allows us to press the Enter key just as we normally do when typing in a LyX document. The key is to use Environment instead of paragraph as LatexType for the style definition of Scrap. Besides, I used the LatexName as wrapsweave, as a LatexName is required by LyX. The definition for wrapsweave is simple: just two empty lines by \par. (If you define it as \newenvironment{wrapsweave}{}{}, you will run into troubles sometimes; especially when you use indent for paragraphs.)

As we know, LaTeX environment cannot be centered in LyX (only paragraphs can), so I defined a special environment ScrapCenter when I want to insert graphics via Sweave and make them center-aligned.

To put all efforts together, this is the new literate-scrap.inc (compare it with http://cran.r-project.org/contrib/extra/lyx/literate-scrap.inc):

Format 2

Preamble
\usepackage{Sweave}
\newenvironment{wrapsweave}{\par}{\par}
EndPreamble

OutputType              literate

Style Scrap
LatexType             Environment
LatexName             wrapsweave
Margin                static
TopSep                0.4
BottomSep             0.4
ParSep                0.0
LabelType             static
Align                 left
AlignPossible         block, left, right, center
NewLine               0
PassThru              1
FreeSpacing           1
TextFont
Color               latex
Family              typewriter
EndFont
End

Style ScrapCenter
LatexType             Environment
LatexName             center
Margin                static
TopSep                0.4
BottomSep             0.4
ParSep                0.0
LabelType             static
Align                 center
NewLine               0
PassThru              1
FreeSpacing           1
TextFont
Color               latex
Family              typewriter
EndFont
End


Enjoy pressing a single Enter key in LyX now! :)

P.S. the side effect of this modification is, your R code will be separated by empty lines. But Sweave will remove blank lines by default, so that is not really a big trouble.

P.P.S. Next time I will write my solution of using pgfSweave in LyX – if you have never tried the pgfSweave package in R, I’d strongly recommend you do it right now!! My comment on this package is: amazingly beautiful!