[R] Combining many dataframes from listings of objects?

[Prof Brian D Ripley]

On Wed, 15 May 2002, Derek Eder wrote:

> I want to combine (rbind) many dataframes into a single data frame, but "automatically" specifying the names of the dataframes as listing of object names.
>
> E.g., combine these 18 df objects into one big df using something conceptually like this :
>
> rbind(objects(pattern="*.df"))

A job for do.call.  I think

do.call("rbind", objects(pattern="*.df"))

might work, and something like it should.

>
>  ...
>
> > objects(pattern="*.df")
>  [1] "BA.Nt1.nREM.APNEA.MIXED.bp.df"       "BA.Nt1.nREM.APNEA.OBSTRUCTIVE.bp.df"
>  [3] "BA.Nt1.nREM.HYPOPNEA.bp.df"          "BA.Nt1.REM.HYPOPNEA.bp.df"
>  [5] "BA.Nt2.nREM.APNEA.MIXED.bp.df"       "BA.Nt2.nREM.APNEA.OBSTRUCTIVE.bp.df"
>  [7] "BA.Nt2.nREM.HYPOPNEA.bp.df"          "BA.Nt2.REM.APNEA.OBSTRUCTIVE.bp.df"
>  [9] "BA.Nt2.REM.HYPOPNEA.bp.df"           "BF.Nt1.nREM.APNEA.MIXED.bp.df"
>
>
>
> By the way in S. I used to do this by creating a large empty target dataframe and then
> looping through the list of objects, write each one into the target.  This is failing in R:
>
> > target_as.data.frame(matrix(data=NA,nrow=8,ncol=14))
> > target[1:4,]__c("a","b","c","d")
>
> > Warning messages:
> 1: invalid factor level, NAs generated in: "[<-.factor"(*tmp*, iseq, value = vjj)
> 2: invalid factor level, NAs generated in: "[<-.factor"(*tmp*, iseq, value = vjj)
> 3: invalid factor level, NAs generated in: "[<-.factor"(*tmp*, iseq, value = vjj)
> 4: invalid factor level, NAs generated in: "[<-.factor"(*tmp*, iseq, value = vjj)
> . . .

You need to set the column types up first.

>
>
> Thank you
>
>
> Derek N. Eder
> Göteborgs Universitet
> Institutionen för klinisk neurovetenskap - psykiatri
> Sahlgrenska universitetssjukhuset SS/SU
> Blå straket 17b
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> derek.eder at neuro.gu.se
>
>
> Gothenburg University
> Institute of Clinical Neuroscience,
> Section for Psychiatry
> Salhgrenska Hospital  SU/SS
> SE 413 45  Göteborg
> Sweden
>
>
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-- 
Brian D. Ripley,                  ripley at stats.ox.ac.uk
Professor of Applied Statistics,  http://www.stats.ox.ac.uk/~ripley/
University of Oxford,             Tel:  +44 1865 272861 (self)
1 South Parks Road,                     +44 1865 272860 (secr)
Oxford OX1 3TG, UK                Fax:  +44 1865 272595

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