Show only selected figures of generated figures in a cache in knitr - r

Question

If I have a chunk that generates 4 figures and I want to keep them all (fig.keep=all), is it possible to show only the second one using a cache option? I see that echo=2:5 can be selected, but it doesn't seem that fig.show=2 is possible. Is the best method to do \includegraphcis{fig2.pdf}?
Thanks.

Answer 1

If you don't want to keep all figures you can simply use :
Use argument fig.keep=c(2,4)
Reproducible example :
\documentclass[a4paper]{article}
\begin{document}
<<load_libraries, echo = FALSE, eval = TRUE, results ="hide">>=
library(knitr)
#
<<multiplefig, fig.keep=c(2,4),fig.height=4,fig.with=10, out.width='.8\\linewidth'>>=
mapply(function(X)plot(X,main=X),c(1:4))
#
\end{document}
However, since you want to keep figures, I would do it the old way in sweave, save the figures using png or pdf.
Reproducible example :
\documentclass[a4paper]{article}
\usepackage{graphicx}
\graphicspath{{figure/}}
\begin{document}
<<multiplefig, echo=FALSE>>=
for (i in 1:4){
png(file=paste0(getwd(),"/figure/fig",i,".png"))
plot(1,1,main=i,cex.main=4)
dev.off()
}
#
This plot shows only figure \ref{fig:fig2} but 4 other are saved
\begin{figure}[htbp]
\centering
\includegraphics[width=0.5\textwidth]{fig2.png}
\caption{}
\label{fig:fig2}
\end{figure}
\end{document}