Re: [O] ob-R, problem with try/catch

[Charles C. Berry]

On Wed, 22 Apr 2015, Rainer M Krug wrote:

> Envoyé de mon iPhone
>
> > Le 23 avr. 2015 à 04:23, Charles C. Berry <address@hidden> a écrit :
> >
> > > On Wed, 22 Apr 2015, Thomas S. Dye wrote:
> > >
> > > Aloha all,
> > >
> > > Prior to eaa3a761dae, when working in a session, I was able to run this
> > > R source code block without problems:
> > >
> > > ,-----------------------------------------
> > > | #+header: :file r/adze_wt_log.pdf
> > > | #+header: :results output graphics
> > > | #+header: :width 4 :height 3
> > > | #+begin_src R
> > > |   g <- ggplot(x, aes(x = weight))
> > > |   g + geom_histogram(aes(y=..density..))
> >
> > ## Try this:
> >
> > print( g + geom_histogram(aes(y=..density..)) ) # before rm(g).
> >
> >
> > > |   rm(g)
> > > | #+end_src
> > > `-----------------------------------------
> > >
> > > After eaa3a761dae, I get an error and an empty output file.
> >
> > That commit introduced a tryCatch() wrapper for graphics results.
> >
> > You probably know that ggplot (or ggplot2) relies on printing of objects to 
> > produce graphics (see R-FAQ 7.22).
> >
> > tryCatch(expr,...) evaluates expr and returns its value, which is `rm(g)' in 
> > your case. But `rm(g)' is not autoprinted, and you get an empty file.
>
> I am not in front of my computer but there must be more, as even before 
> the commit there should have been empty file for exactly the same 
> reason.

`:results output' will return the autoprinted values. Without tryCatch it 
works.


> Also, the error is strange. Could you send a small reproducable example, 
> so that we can see which error you get? Because if you get an error and 
> an empty file, an error must be in the tryCatcb block.

Here are two blocks that differ in using tryCatch. The first produces an 
empty, malformed pdf. The second produces a valid pdf. If you comment out 
the `invisible()' line in the first, then both will produce similar valid 
pdf's.

#+header: :file nada.pdf
#+header: :results output graphics
#+header: :width 4 :height 3
#+begin_src R
  require(ggplot2)
  df <-
      data.frame(gp = factor(rep(letters[1:3], each = 10)),
                 y = rnorm(30))
  ggplot(df, aes(x = gp, y = y)) + geom_point()
  invisible()
#+end_src


#+BEGIN_SRC R :results output
  require(ggplot2)
  pdf(file="aok.pdf",width=4,height=3)
  df <-
      data.frame(gp = factor(rep(letters[1:3], each = 10)),
                 y = rnorm(30))
  ggplot(df, aes(x = gp, y = y)) + geom_point()
  invisible()
  dev.off()
#+END_SRC



HTH,

Chuck