made docstrings clearer and more explicit/correct for eval and R methods

IPython/extensions/rmagic.py

@@ -188,13 +188,13 b' class RMagics(Magics):'
         Returns the output to R's stdout() connection, and 
         the value generated by evaluating the code (see below)
         
-        In line mode (ie called with %R <stuff>), behavior
-        is unchanged, returns a python object representing
-        the final value, suitable for assignment into a 
-        python variable.
+        In line mode (ie called with %R <stuff>), resulting
+        values are not printed (explicit calls to the 
+        show/print R functions still result in properly
+        captured R output).
 
         In cell mode (called with %%R ...), behavior
-        now reproduces the REPL behavior of the R
+        reproduces the REPL behavior of the R
         interpreter (which agrees with how cells of
         python code are handled by the notebook).
 
@@ -204,8 +204,8 b' class RMagics(Magics):'
         invisibly, the value will be printed using the
         show R function.
 
-        Actual evaluation of R code is done via a call
-        of the form withVisible({<code>})
+        Actual evaluation of R code is done via an R
+        call of the form withVisible({<code>})
         
         '''
         old_writeconsole = ri.get_writeconsole()
@@ -436,12 +436,13 b' class RMagics(Magics):'
             In [9]: %R X=c(1,4,5,7); sd(X); mean(X)
             Out[9]: array([ 4.25])
 
-        As a cell, this will run a block of R code, without bringing anything back by default::
+        As a cell, this will run a block of R code. By default the resulting value
+        is printed if it would be when evaluating the same code within an R REPL.
+        Nothing is returned to python by default.
 
             In [10]: %%R
                ....: Y = c(2,4,3,9)
-               ....: print(summary(lm(Y~X)))
-               ....:
+               ....: summary(lm(Y~X))
 
             Call:
             lm(formula = Y ~ X)