[Babel][R] buffer-wide and code block specific use of :session

[Bernd Weiss <bernd.weiss@uni-koeln.de>]

Org-mode version 7.4 (release_7.4.348.g6132)


Dear all,

I am preparing a document which contains text and R code/output. In 
particular, I'd like to print out a (correlation) matrix. This is my 
org-mode document (I intentionally have two code blocks):

#----------------------------------------------------------
#+ Does not work

#+BABEL: :session *R*
#+BEGIN_SRC R :results silent :tangle simcorrdata.R
cormat <- c(1.0,  0.2,  0.4,
             0.2,  1.0, -0.3,
             0.4, -0.3,  1.0)
cormat <- matrix(cormat, ncol = 3, byrow = TRUE)
#+END_SRC

So, the correlation matrix looks as follows:

#+BEGIN_SRC R :exports both :tangle simcorrdata.R
print(cormat)
#+END_SRC
#----------------------------------------------------------

Since I have two code blocks, I need to use :session. If I define 
:session buffer-wide as

#+BABEL: :session *R*

then the matrix cormat is unknown within the second code block ("object 
'cormat' not found"). However, if I specify :session for each code block 
seperately then it works as expected.

#----------------------------------------------------------
#+ Does work

#+BEGIN_SRC R :session :results silent :tangle simcorrdata.R
cormat <- c(1.0,  0.2,  0.4,
             0.2,  1.0, -0.3,
             0.4, -0.3,  1.0)
cormat <- matrix(cormat, ncol = 3, byrow = TRUE)
#+END_SRC

So, the correlation matrix looks as follows:

#+BEGIN_SRC R :session :exports both :tangle simcorrdata.R
print(cormat)
#+END_SRC
#----------------------------------------------------------


Does this happen due to my poor understanding of the :session argument? 
Or is this a bug?

Thanks for your help,

Bernd