[R] Recoding Multiple Variables in a Data Frame in One Step

[William Dunlap]

> -----Original Message-----
> From: r-help-bounces at r-project.org [mailto:r-help-bounces at r-project.org] On Behalf Of William Dunlap
> Sent: Monday, July 25, 2011 3:49 PM
> To: David Winsemius; Anthony Damico
> Cc: r-help at r-project.org
> Subject: Re: [R] Recoding Multiple Variables in a Data Frame in One Step
> 
> > -----Original Message-----
> > From: r-help-bounces at r-project.org [mailto:r-help-bounces at r-project.org] On Behalf Of David
> Winsemius
> > Sent: Monday, July 25, 2011 3:39 PM
> > To: Anthony Damico
> > Cc: r-help at r-project.org
> > Subject: Re: [R] Recoding Multiple Variables in a Data Frame in One Step
> >
> >
> > On Jul 21, 2011, at 8:06 PM, Anthony Damico wrote:
> >
> > > Hi, I can't for the life of me find how to do this in base R, but
> > > I'd be
> > > surprised if it's not possible.
> > >
> > > I'm just trying to replace multiple columns at once in a data frame.
> > >
> > > #load example data
> > > data(api)
> > >
> > > #this displays the three columns and eight rows i'd like to replace
> > > apiclus1[ apiclus1$meals > 98 , c( "pcttest" , "api00" ,
> > > "sch.wide" ) ]
> > >
> > >
> > > #the goal is to replace pcttest with 100, api100 with NA, and
> > > sch.wide with
> > > "Maybe"
> > >
> > > #this doesn't work--
> > > apiclus1[ apiclus1$meals > 98 , c( "pcttest" , "api00" ,
> > > "sch.wide" ) ] <-
> > > c( 100 , NA , "Maybe" )
> 
> Try list(pcttest=100, api00=NA, sch.wide="Maybe") instead
> of c(100, NA, "Maybe") as the new value.

Note that the names in the replacement list are ignored,
so it might be best to omit them (in case seeing the names
makes someone think they can give the replacement value in
any order as long as they get the names right).

> 
> Here is a self-contained example
>  > df <- data.frame(Size=sin(1:10), Name=state.name[11:20], Value=11:20, stringsAsFactors=FALSE)
>  > df[df$Size<0, c("Name", "Value")] <- list(Name="JUNK", Value=-99)

df[df$Size<0, c("Name", "Value")] <- list("JUNK", -99)

>  > df
>           Size      Name Value
>  1   0.8414710    Hawaii    11
>  2   0.9092974     Idaho    12
>  3   0.1411200  Illinois    13
>  4  -0.7568025      JUNK   -99
>  5  -0.9589243      JUNK   -99
>  6  -0.2794155      JUNK   -99
>  7   0.6569866  Kentucky    17
>  8   0.9893582 Louisiana    18
>  9   0.4121185     Maine    19
>  10 -0.5440211      JUNK   -99
> 
> Bill Dunlap
> Spotfire, TIBCO Software
> wdunlap tibco.com
> 
> > >
> > > #the results replace downward instead of across
> > > apiclus1[ apiclus1$meals > 98 , c( "pcttest" , "api00" ,
> > > "sch.wide" ) ]
> >
> > If I had noted that I would have tried this:
> >
> > apiclus1[ apiclus1$meals > 98 , rep( c( "pcttest" , "api00" ,
> > "sch.wide" ),
> >                                         each =  sum(apiclus1$meals > 98)
> >                                      ) ]
> >
> > Should be pretty easy to test, but since _you_ are the one responsible
> > for providing examples for testing when posting to rhelp,  I am going
> > to throw an untested theory back at you.
> >
> >
> > >
> > > I know I can do this with a few more steps (like one variable at a
> > > time or
> > > by counting the number of rows to replace and then using rep() ..but
> > > I'm
> > > hoping there's a quicker way?
> > >
> > >
> > > Thanks!!
> > >
> > > Anthony Damico
> >
> >
> > David Winsemius, MD
> > West Hartford, CT
> >
> > ______________________________________________
> > 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.
> 
> ______________________________________________
> R-help at r-project.org mailing list
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> PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.