Thanks, Bill.
Andrew
On Thu, Feb 07, 2013 at 09:21:53PM +0000, William Dunlap wrote:
> >> Notice that the '[[' function is superior in every way to the '$'
> >> function.
> > I'm curious to know whether you can point to some consolidated comparison?
>
> Two problems are that List$name allows abbreviations of name and does not
> allow
> variable names.
>
> With List$name you get:
> > List <- list(Eleven=11, Twelve="xii")
> > str(List)
> List of 2
> $ Eleven: num 11
> $ Twelve: chr "xii"
> > List$E # $ accepts abbreviations, which might seem nice
> [1] 11
> > List$E <- List$E + 100 # but can bite you in replacements
> > str(List) # Eleven not incremented, new E created
> List of 3
> $ Eleven: num 11
> $ Twelve: chr "xii"
> $ E : num 111
> > nm <- "Twelve" # want to use component named variable
> > List$nm # no component named "nm"
> NULL
> > eval(parse(text=paste0("List", "$", nm))) # ugly dangerous hack
> [1] "xii"
> > eval(call("$", quote(List), nm)) # ugly safe hack
> [1] "xii"
>
> With List[["name"]] syntax you get
> > List <- list(Eleven=11, Twelve="xii")
> > List[["E"]]
> NULL
> > List[["E"]] <- List[["E"]] + 100
> > str(List)
> List of 3
> $ Eleven: num 11
> $ Twelve: chr "xii"
> $ E : num(0)
> > List[["Eleven"]] <- List[["Eleven"]] + 100
> > str(List)
> List of 3
> $ Eleven: num 111
> $ Twelve: chr "xii"
> $ E : num(0)
> > nm <- "Twelve"
> > List[[nm]]
> [1] "xii"
>
> Bill Dunlap
> Spotfire, TIBCO Software
> wdunlap tibco.com
>
>
> > -----Original Message-----
> > From: r-help-boun...@r-project.org [mailto:r-help-boun...@r-project.org] On
> > Behalf
> > Of Andrew Robinson
> > Sent: Thursday, February 07, 2013 12:52 PM
> > To: David Winsemius
> > Cc: r-help
> > Subject: Re: [R] why "object 'x' not found"?
> >
> > Hi David,
> >
> > The following is an interesting observation ...
> >
> > On Friday, February 8, 2013, David Winsemius wrote:
> >
> > >
> > > On Feb 7, 2013, at 10:20 AM, Winfried Moser wrote:
> > > ....
> > >
> > Notice that the '[[' function is superior in every way to the '$' function.
> > >
> >
> > I'm curious to know whether you can point to some consolidated comparison?
> >
> > Best wishes,
> >
> > Andrew
> >
> >
> > --
> > Andrew Robinson
> > Director (A/g), ACERA
> > Department of Mathematics and Statistics Tel: +61-3-8344-6410
> > University of Melbourne, VIC 3010 Australia (prefer email)
> > http://www.ms.unimelb.edu.au/~andrewpr Fax: +61-3-8344-4599
> > http://www.acera.unimelb.edu.au/
> >
> > FAwR: http://www.ms.unimelb.edu.au/~andrewpr/FAwR/
> > SPuR: http://www.ms.unimelb.edu.au/spuRs/
> >
> > [[alternative HTML version deleted]]
> >
> > ______________________________________________
> > R-help@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.
--
Andrew Robinson
Director (A/g), ACERA
Department of Mathematics and Statistics Tel: +61-3-8344-6410
University of Melbourne, VIC 3010 Australia (prefer email)
http://www.ms.unimelb.edu.au/~andrewpr Fax: +61-3-8344-4599
http://www.acera.unimelb.edu.au/
Forest Analytics with R (Springer, 2011)
http://www.ms.unimelb.edu.au/FAwR/
Introduction to Scientific Programming and Simulation using R (CRC, 2009):
http://www.ms.unimelb.edu.au/spuRs/
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