I need to change the background of all tiff images produced by my R Sweave document and encountered the same problem as described here:
Respecting global options in knitr
but with par(bg = ), which supposedly is working according to a comment.
MWE:
\documentclass{article}
\begin{document}
<<setup, cache = FALSE>>=
opts_chunk$set(dev = c('pdf','tiff'))
opts_knit$set(global.par = TRUE)
par(bg='cyan')
@
<<>>=
plot (3,3)
@
\end{document}
(I'm not allowed to comment or I would have stayed on that post.)
I also tried using a hook, based on the example here: https://github.com/yihui/knitr/blob/master/inst/examples/knitr-graphics.Rnw
knit_hooks$set(par=function(before, options, envir){
if (before) par(bg='cyan')
})
but that didn't work either.
The only thing that works is to set the parameter in every chunk, for example:
<<test, dev = 'tiff'>>=
par(bg = 'cyan')
plot(3,2)
@
(I actually want a white background but it's easier to test with a color. Not my choice to use TIFF btw.)
Any ideas on what's going on?
The MWE presented does not imply that global.par doesn't work for bg. The reason why the plot doesn't use the specified background color is that global.par = TRUE affects only the subsequent chunks.
Knitr's settings must be set in a chunk before any chunks which rely on those settings to be active. [source]
You cannot rely on a global option to be apply in the chunk you set it.
The following example demonstrates that setting the background color in a later chunk makes the plot use it:
\documentclass{article}
\begin{document}
<<setup, cache = FALSE>>=
opts_knit$set(global.par = TRUE)
@
<<>>=
par(bg='cyan')
@
<<>>=
plot (3,3)
@
\end{document}