Hi Francesco, This is an advanced topic in knitr; it is called a chunk hook: http://yihui.name/knitr/hooks
Sorry for the confusion on the name "par"; you can call it anything, e.g. mypar knit_hooks$set(mypar = function(before, options, envir) { if (before) par(mar = c(4, 4, .1, .1)) }) opts_chunk$set(mypar = TRUE) For par(bg=rgb(runif(1), runif(1), runif(1))), it is nothing but a line of normal R code. Regards, Yihui -- Yihui Xie <xieyi...@gmail.com> Phone: 515-294-2465 Web: http://yihui.name Department of Statistics, Iowa State University 2215 Snedecor Hall, Ames, IA On Wed, Jan 9, 2013 at 2:59 AM, Francesco Sarracino <f.sarrac...@gmail.com> wrote: > Dear Yihui, > > thanks a lot for your kind reply. Your solution is very elegant and > versatile. > However, there is a point that is obscure to me and I didn't manage to fully > understand them after looking at the Knitr manual and graphic manual. > The issue concerns the hook: > > knit_hooks$set(par = function(before, options, envir) { > if (before) par(mar = c(4, 4, .1, .1)) > }) > > why do you set par as a function? > moreover, below you write: > > par(bg=rgb(runif(1), runif(1), runif(1))) > > does this mean that before = rgb(runif(1)); options = runif(1) and envir = > runif(1) ? > > and what does this produce? I don't understand what's going on, can you > please help me or address me to some documentation? > > thanks in advance for your kind help, > f. > ______________________________________________ R-help@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.