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

[Henrik Bengtsson]

library("R.oo");

setMethodS3("ll", "character", function(pathname, ..., force=FALSE) {
  require("R.cache") || throw("Package not loaded: R.cache");

  # Argument 'pathname':
  pathname <- Arguments$getReadablePathname(pathname, mustExist=TRUE);

  # Check for cache results
  fi <- file.info(pathname);
  rownames(fi) <- NULL;
  key <- list(fileInfo=fi, checksum=digest::digest(pathname, file=TRUE));
  res <- loadCache(key=key);
  if (!force && !is.null(res)) {
    return(res);
  }

  # Load the actual data
  env <- loadToEnv(pathname);

  # List its content
  res <- ll(..., envir=env);

  # Clean up
  rm(env);

  # Save to cache
  saveCache(res, key=key);

  res;
})


example(iris);
save.image("foo.RData");
ll("foo.RData");

        member data.class dimension objectSize
1         dni3       list         3        392
2           ii data.frame  c(150,5)       6424
3 ll.character   function      NULL       6948

/H

On Sat, Dec 19, 2009 at 12:14 AM, Patrick Connolly
<p_connolly at slingshot.co.nz> wrote:
> 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
>
> ~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.
>
> ______________________________________________
> R-help at r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
>