LaTeX figure label from R plot using KnitR?

knitr, latex, r

Solution

You need to set `fig.cap = ''` (or whatever you wish) to ensure that a figure environment is used in the `latex` document. (you may have noticed that the `\begin{figure} ... \end{figure}` is missing along with the `\label{}` component

eg

\documentclass[12pt, english, oneside]{amsart}
\begin{document}
See Figure \ref{fig:plot}.
<<plot, fig.lp="fig:", fig.cap = ''>>=
plot(x=0, y=0)
@
\end{document}

I would agree that the description from the website is less than clear as to this being necessary.

fig.env: ('figure') the LaTeX environment for figures, e.g. set fig.env='marginfigure' to get \begin{marginfigure}

fig.cap: (NULL; character) figure caption to be used in a figure environment in LaTeX (in \caption{}); if NULL or NA, it will be ignored, otherwise a figure environment will be used for the plots in the chunk (output in \begin{figure} and \end{figure})

Although the graphics manual is clear, and the reasoning makes sense

Figure Caption

If the chunk option fig.cap is not NULL or NA, the plots will be put in a figure environment when the output format is LATEX, and this option is used to write a caption in this environment using \caption{}. The other two related options are fig.scap and fig.lp which set the short caption and a prefix string for the figure label. The default short caption is extracted from the caption by truncating it at the first period or colon or semi-colon. The label is a combination of fig.lp and the chunk label. Because figure is a float environment, it can float away from the chunk output to other places such as the top or bottom of a page when the TEX document is compiled.

If you were wishing to replicate a `R` session output, you wouldn't want the figures to float away from the line of code which defines how they were created.

Problem

I can't get R/KnitR to create the LaTeX `\label{}` statement for a figure. The manual seems to indicate that a `\label{}` statement will be created by concatenating the string in fig.lp ("fig:" by default) with the label for the R-code chunk. I haven't been able to get this to work, however. No `\label{}` statement is created for the first figure created by knitting the MWE below. The second figure has it's label added with a workaround that I just discovered, putting the R chunk in a figure environment, and putting the `\label` tag after or inside the `\caption` tag. ``` \documentclass[12pt, english, oneside]{amsart} \begin{document} Figure \ref{fig:plot} doesn't have it's label. <<plot>>= plot(x=0, y=0) @ Figure \ref{fig:plot2} has its label. \begin{figure} \caption{\label{fig:plot2}} <<>>= plot(x=1,y=1) @ \end{figure} \end{document} ``` Okay, I've found a workaround by putting the R chunk in a `\begin{figure} . . .\end{figure}` environment in LaTeX. I can create the label in that same environment. Still, I'd like to understand how Yihui intends for this to be handled with KnitR.

Original source