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 can work around this error by removing the line "rm(g)",
Right. Then, the expression returned by tryCatch is
g + geom_histogram(aes(y=..density..))
which is autoprinted giving the graph.
When in doubt, there is no harm in explicitly print()ing objects that
would have been autoprinted otherwise.
For reference, here is what org-babel-execute:R produces for your src
block (lightly formatted for readability):
#+BEGIN_SRC R
pdf(file=\"r/adze_wt_log.pdf\",width=4,height=3)
tryCatch({
g <- ggplot(x, aes(x = weight))
g + geom_histogram(aes(y=..density..))
rm(g)
},
error=function(e){
plot(x=-1:1, y=-1:1, type='n', xlab='', ylab='',
axes=FALSE)
text(x=0, y=0, labels=e$message, col='red')
paste('ERROR', e$message, sep=' : ')})
dev.off()
#+END_SRC
HTH,
Chuck
