# [Rcpp-devel] Maximum Columns in Rcpp DataFrame (revisited)

Kevin Ushey kevinushey at gmail.com
Tue Jul 8 23:49:09 CEST 2014

Maybe we need a DataFrameBuilder class that someone could use like so:

DataFrame df = DataFrameBuilder::create()

This could be made as a generic VectorBuilder<T> class as well.

Or maybe I've been writing too much Java lately...

Cheers,
Kevin

On Tue, Jul 8, 2014 at 2:43 PM, Steffen Neumann <sneumann at ipb-halle.de>
wrote:

> Hi,
>
> thanks for the quick answer. I didn't find how to *easily*
> populate my list with named elements without fiddling
> with the names attribute, so I ended up creating
> two dataframes and then cbinding them from within C++
>
>
> Yours,
> Steffen
>
> On Di, 2014-07-08 at 11:17 -0500, Dirk Eddelbuettel wrote:
> > On 8 July 2014 at 17:51, Steffen Neumann wrote:
> > | Hi,
> > |
> > | I (think I) need to create a DataFrame with more than 20 entries,
> > | because I want another slot in this file:
> > | https://github.com/sneumann/mzR/blob/master/src/RcppRamp.cpp#L221
> > |
> > | I stumbled upon a 2year old answer here:
> > |
> > |
> http://lists.r-forge.r-project.org/pipermail/rcpp-devel/2013-March/005430.html
> > |
> > | Questions:
> > |
> > | 1) Should I avoid DataFrame here in first place ? I'd love to keep it
> > | 2) Is there a more elegant solution for >20 entries by now ?
> > | 3a) How do I create the mentioned "local header file with 21, 22, 23,
> ... \infty arguments as you need it."
> > | 3b) How and where do I #include that ? I need to fake a directory
> structure
> > |     so that <Rcpp/DataFrame.h> picks up my version of #include
> <Rcpp/generated/DataFrame_generated.h> ?
> > | 4) Is that future proof ?!
> >
> > No.
> >
> > Can you 'fudge it' and just create a List with N elements, each
> containing a
> > DataFrame of 10 columns?  You can then find them in R at the end ...
> >
> > Come to think of it, a DataFrame is _almost_ the same as a list, so I
> would
> > just create a List with your desired 20+ elements and then just call
> > as.data.frame() on it.
> >
> > Or in case all entries are numeric (you didn't say..) just take a
> matrix...
> >
> > Dirk
> >
>
>
> --
> IPB Halle                    AG Massenspektrometrie & Bioinformatik
> Dr. Steffen Neumann          http://www.IPB-Halle.DE
> Weinberg 3                   http://msbi.bic-gh.de
> 06120 Halle                  Tel. +49 (0) 345 5582 - 1470
>                                   +49 (0) 345 5582 - 0
> sneumann(at)IPB-Halle.DE     Fax. +49 (0) 345 5582 - 1409
>
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