[R] What is the fastest way to see what are in an RData file?

[Patrick Connolly]

On Sat, 19-Dec-2009 at 09:24AM +1800, Peng Yu wrote:

|> On Sat, Dec 19, 2009 at 3:35 AM, Patrick Connolly
|> <p_connolly at slingshot.co.nz> wrote:
|> > On Thu, 17-Dec-2009 at 03:13PM +1800, Peng Yu wrote:
|> >
|> > |> Currently, I load the RData file then ls() and str(). But loading the file
|> > |> takes too long if the file is big. Most of the time, I only interested what
|> > |> the variables are in the the file and the attributes of the variables (like
|> > |> if it is a data.frame, matrix, what are the colnames/rownames, etc.)
|> > |>
|> > |> I'm wondering if there is any facility in R to help me avoid loading the
|> > |> whole file.
|> >
|> >
|> > I have a pretty nifty way of seeing what's in such a file, but I still
|> > have to load all of the binary file before I can do so.  If it's
|> > taking you such a long time, maybe you could keep a larger number of
|> > smaller RData files.
|> 
|> What is your 'nifty way'? 

Well, it's nifty to may way of thinking.  It's not particularly nifty
in how I wrote it, but what it achieves is pretty nifty.  I know
thousands would disagree, but I think this is nifty:

         Object     Mode   Rows Cols Len    Date   
 1 fix.bill      function   --   --    1 22/12/2008
 2 fix.bill2     function   --   --    1 22/12/2008
 3 aa            dataframe  9    1     1 21/12/2008
 4 bb            dataframe  9    6     6 21/12/2008
 5 bill.lines    dataframe  759  1     1 21/12/2008
 6 aftertax5     function   --   --    1 31/08/2008
 7 aftertax6     function   --   --    1 31/08/2008
 8 cont.cgt6     function   --   --    1 31/08/2008
 9 aftertax5BW   function   --   --    1 29/08/2008
10 cont.cgt      function   --   --    1 29/08/2008
11 summ.df       dataframe  2    5     5 29/08/2008


Part of the reason why it's not that well-written is because it was
first written for SPlus which works rather differently from R in
important respects, and at the time I knew quite a lot less than I
know now.  It's not exactly in publishable form since it uses a number
of my local (inelegant) functions and it would not work on Windows
without some fundamental rewriting.  I did the minimum to port if from
Splus and gave no thought whatever to having it work on Windows.

On two occasions I offered to supply my code to anyone who wanted
something to start with to make something publishable, but hardly
anybody was impressed with what I thought was nifty.  (I never made it
as a singer-songwriter either.) :-)

|>      How fast is it?

Practically no time (milliseconds) to run the function, but the binary
file must be fully loaded, and that's what you're trying to avoid, so
it wouldn't fit your purpose.


-- 
~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.   
   ___    Patrick Connolly   
 {~._.~}                   Great minds discuss ideas    
 _( Y )_  	         Average minds discuss events 
(:_~*~_:)                  Small minds discuss people  
 (_)-(_)  	                      ..... Eleanor Roosevelt
	  
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